Charging system for mobile robot, method for searching charging station, mobile robot, connector, and electrical connection structure Number:6,764,373 from the United States Patent and Trademark Office (PTO) owispatent

Title: Charging system for mobile robot, method for searching charging station, mobile robot, connector, and electrical connection structure

Abstract: A charging system for a mobile robot includes the mobile robot that is battery-driven and moves in a self-controlled way within a work space, and a charging station for accommodating the mobile robot for a battery charging operation. The charging system includes visible recognition data arranged in a predetermined location of the charging station, an image pickup unit mounted on the mobile robot, a calculating unit for calculating a range and a bearing from the mobile robot to the charging station, based on an image picked up by the image pickup unit, and a searching unit for causing the mobile robot to search for the charging station, based on the calculation result provided by the calculating unit. Since the mobile robot searches for the charging station using a camera for recognizing the visible recognition data, a charging operation is automated.

Patent Number: 6,764,373 Issued on 07/20/2004 to Osawa,   et al.

---

Inventors:	Osawa; Hiroshi (Kanagawa, JP), Hosonuma; Naoyasu (Saitama, JP)
Assignee:	Sony Corporation (Tokyo, JP)
Appl. No.:	09/698,566
Filed:	October 27, 2000

---

Foreign Application Priority Data

---

Oct 29, 1999 [JP]			11-308224

Current U.S. Class:	446/175 ; 180/169; 318/587; 446/454; 446/484
Current International Class:	A63H 11/00 (20060101); A63H 11/18 (20060101)
Field of Search:	318/587,568.11 701/23,24,25 446/484,454,456,175 700/245 180/169,168,167 439/924.1,668,669,736,22,24,25,675

---

References Cited [Referenced By]

---

U.S. Patent Documents

	1103250		July 1914		Benjamin
	4777416		October 1988		George et al.
	5220263		June 1993		Onishi et al.
	5440216		August 1995		Kim
	5466181		November 1995		Bennett et al.
	5869910		February 1999		Colens
	5892350		April 1999		Yoshikawa
	5995884		November 1999		Allen et al.
	6030229		February 2000		Tsutsui
	6074230		June 2000		Comerci et al.
	6429016		August 2002		McNeil
	6453055		September 2002		Fukumura et al.
	6456728		September 2002		Doi et al.
	6480761		November 2002		Ueno et al.

Foreign Patent Documents

	03284102		Dec., 1991		JP
	05023264		Feb., 1993		JP
	07191755		Jul., 1995		JP
	2001125641		May., 2001		JP

Other References

Rubenstein, Roy, "Be afraid . . . future dominance of robots", Mar. 12, 1997, Electronics Weekly, n1804, p. 16(2).* . Hada, Y.; Yuta, S., "Robust navigation and battery re-charging system for long term activity of autonomous mobile robot", 1999 Proceedings of the Ninth International Conference on Advanced Robotics. 99 ICAR, Tokyo, Japan, p. 297-302.* . Dudar, A. M.; Wagner, D. G.; Teese, G. D., "Mobile autonomous robot for radiological surveys", Westinghouse Savannah Rive Co., Aiken, SC, 1992, 12p.* . Dudar, e.; Teese, G.;Wagner, D., "SIMON: A mobile robot for floor contamination surveys", Westinghouse Savannah River Co Aiken, SC, 1991, 11p..

Primary Examiner: Banks; Derris H.
Assistant Examiner: Ceglelnik; Urazula M
Attorney, Agent or Firm: Frommer Lawrence & Haug LLP Frommer; William S. Simon; Darren M.

---

Claims

---

What is claimed is:

1. A charging system for a mobile robot comprising the mobile robot that is battery-driven and moves in a self-controlled way within a work space, and a charging station for accommodating the mobile robot for a battery charging operation, the mobile robot being of the at least four-footed type which walks like an animal and has a power connector on the abdomen of a torso unit thereof, the charging system comprising: a concave receptacle with a power connector on the inner bottom portion of the receptacle; wherein the receptacle supports the mobile robot in a lying down position; visible recognition data arranged in a predetermined location of the charging station; image pickup means mounted on the mobile robot; calculating means for calculating a range and a bearing from the mobile robot to the charging station, based on an image picked up by the image pickup means; and searching means for causing the mobile robot to search for the charging station, based on the calculation result provided by the calculating means.

2. A charging system according to claim 1, further comprising communication means for performing data exchange between the mobile robot and the charging station.

3. A charging system according to claim 1, wherein the visible recognition data is a print medium glued onto the surface of the charging station.

4. A charging system according to claim 1, wherein the visible recognition data is formed on a print medium, and a plurality of print media is glued onto the surface of a three-dimensional object.

5. A charging system according to claim 1, wherein the visible recognition data is displayed on a screen of a display unit.

6. A charging system according to claim 1, wherein the visible recognition data is displayed on a screen of a display unit, and is dynamically used in a manner that prevents the visible recognition data from being merged into the environment of the work space.

7. A charging system according to claim 1, wherein the visible recognition data is displayed on a screen of a display unit and is changed in response to a range from the mobile robot.

8. A charging system according to claim 1, wherein the visible recognition data is a combination of colors and patterns.

9. A charging system according to claim 1, wherein the visible recognition data is a two-dimensional bar code.

10. A charging system according to claim 1, wherein the visible recognition data is arranged on an elevated portion of the charging station.

11. A charging system according to claim 1, wherein at least one of the charging station and the mobile robot comprises an indicator indicating the condition of a battery.

12. A charging system according to claim 1, wherein the charging station further comprises transmitter means that transmits at least one of light ray, infrared ray, sound wave, ultrasonic wave, radio wave, and magnetic field, the mobile robot comprises receiver means for receiving the wave transmitted from the transmitter means, and wherein the calculating means calculates the range and the bearing from the mobile robot to the charging station, based on at least one of the image provided by the image pickup means and data received by the receiver means.

13. A charging system according to claim 12, wherein the wave transmitted by the transmitter means is easily discriminated and separated from other signals created within the work space.

14. A charging system according to claim 1, wherein the mobile robot comprises a head unit which performs a scanning motion with respect to a torso unit, and at least one of the image pickup means and the receiver means is arranged on the head unit.

15. A charging system according to claim 12, wherein the transmitter means transmits at least two signal waves, from among light ray, infrared ray, sound wave, ultrasonic wave, radio wave, and magnetic field, and the receiver means switches the received signal in response to the range between the charging station and the mobile robot.

16. A charging system according to claim 12, wherein the transmitter means projects light ray through a slit, and changes the pattern of the slit depending on the direction of light projection.

17. A charging system according to claim 12, wherein the transmitter means transmits at least two signal waves that are different in output intensity and frequency component.

18. A charging system according to claim 1, wherein the charging station comprises communication means for exchanging data with a device other than the devices of the charging system.

19. A charging system according to claim 12, wherein the transmitter means transmits is arranged external to the charging station.

20. A charging system according to claim 1, wherein the charging station comprises, on the wall thereof, color patterns painted in at least two colors, and the mobile robot searches for the charging station, based on the positional relationship of the color patterns in an image provided by the image pickup means.

21. A charging system according to claim 1, wherein the mobile robot is of the four-footed type which quadrupedally walks like a dog, and comprises a power connector on the hip portion of the torso unit thereof, the charging station comprises a receptacle with a bowl-shaped concave, and a generally semi-spherical projection on the generally central position of the bowl-shaped concave, and the receptacle supports the mobile robot in the sitting position thereof.

22. A charging system according to claim 1, wherein the mobile robot is of the four-footed type which quadrupedally walks like a dog, and comprises a power connector on the hip portion of the torso unit thereof, the charging station comprises a receptacle with a bowl-shaped, rotationally symmetric concave, and a generally semi-spherical, rotationally symmetric projection on the generally central position of the bowl-shaped concave, and the receptacle supports the mobile robot in the sitting position thereof at any angle.

23. A charging system according to claim 1, wherein the mobile robot has a tapered portion on at least one of a head unit, and shoulders and hip portions of a torso unit, and the charging station comprises a generally U-shaped structure having an inner wall which receives the tapered portion formed on the mobile robot.

24. A charging system according to claim 1, wherein the mobile robot has a tapered portion on at least one of a head unit, and shoulders and hip portions of a torso unit, and the charging station comprises a generally U-shaped structure having an inner wall which receives the tapered portion formed on the mobile robot, and on the deepest inside position of the U-shaped structure, a lip having a connector arranged on the top surface thereof.

25. A charging system according to claim 1, wherein the mobile robot has a tapered portion on at least one of a head unit, and shoulders and hip portions of a torso unit, and the charging station comprises a generally U-shaped structure having an inner wall which receives the tapered portion formed on the mobile robot, and on the deepest inside position of the U-shaped structure, a lip having a connector arranged on the top surface thereof, and each terminal of the connector extends inwardly deeply into the U-shaped structure.

26. A charging system according to claim 1, wherein the mobile robot is ambulatory, and an electrode terminal is arranged on the sole of at least one foot.

27. A charging system according to claim 1, further comprising at least one electromagnet for generating a magnetic field that connects and disconnects the connector of the mobile robot to and from the connector of the charging station.

28. A charging system according to claim 1, wherein the charging station comprises a drive mechanism for placing the mobile robot in an appropriate engagement position therewith.

29. A charging system according to claim 1, wherein the charging station comprises a generally U-shaped structure that receives the mobile robot, and grip means for gripping the mobile robot within the U-shaped structure.

30. A charging system according to claim 1, wherein the charging station comprises a generally U-shaped structure that receives the mobile robot, and grip means for gripping the mobile robot within the U-shaped structure, and wherein the charging station is used as a carrying case with the mobile robot gripped therewith in.

31. A charging system according to claim 1, wherein the mobile robot is of the type that quadrupedally walks like a dog, and the charging station has a kennel-like configuration, and at least one connector is arranged on the inner wall of the charging station.

32. A method for searching for a charging station, based on a signal wave transmitted by a transmitter arranged external to the charging station in a charging system comprising a mobile robot that is battery-driven and moves in a self-controlled way within a work space, and the charging station for accommodating the mobile robot for a battery charging operation, the mobile robot being ambulatory and having at least a torso unit and at least two foot units, comprising an electrode terminal for power feeding, on one of the abdomen of the torso unit and the back of the torso unit, the method comprising the steps of: teaching the position of the charging station based on the signal wave from the transmitter after the mobile robot has been placed on the charging station, and searching for the charging station by calculating the range and bearing to the charging station, based on the signal wave from the transmitter, with the mobile robot at any position within the work space.

33. A method for searching for a charging station, based on a signal wave transmitted by a transmitter arranged external to the charging station in a charging system comprising a mobile robot that is battery-driven and moves in a self-controlled way within a work space, and the charging station for accommodating the mobile robot for a battery charging operation, the mobile robot being ambulatory and having at least a torso unit and at least two foot units, comprising an electrode terminal for power feeding, on one of the abdomen of the torso unit and the back of the torso unit, the method comprising the steps of: storing beforehand, in a memory of the mobile robot, the position information of the charging station with respect to a reference position set in accordance with the position of the transmitter, and searching for the charging station by calculating the position of the mobile robot with respect to the reference position, based on the signal wave from the transmitter with the mobile robot at any position within the work space, and reading the position information from the memory to calculate the range and the bearing to the charging station.

34. A method for searching for a charging station, based on a signal wave transmitted by a transmitter arranged external to the charging station in a charging system comprising a mobile robot that is battery-driven and moves in a self-controlled way within a work space, and the charging station for accommodating the mobile robot for a battery charging operation, the mobile robot being ambulatory and having at least a torso unit and at least two foot units, comprising an electrode terminal for power feeding, on one of the abdomen of the torso unit and the back of the torso unit, the method comprising: a calculating step in which the mobile robot calculates the position thereof with respect to a reference position set in accordance with the position of the transmitter, based on the signal wave from the transmitter, in the calculating step the charging station calculates the position thereof with respect to the reference position, based on the signal wave from the transmitter, a communication step in which the charging station communicates the position information thereof to the mobile robot, and a searching step in which the mobile robot searches for the charging station by calculating the range and bearing to the charging station through a relative relationship between the position information.

---

Description

---

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a mobile robot which generally or partly imitates living mechanisms of human beings or animals and, particularly, to a mobile robot which bipedally or quadrupedally freely walks or crawls (in a trackless manner) within a work area or space.

The present invention also relates to a mobile robot that is driven by a rechargeable battery with no umbilical power cable connected, and freely and tracklessly moves within a work space, and to a charging mechanism for charging a battery in the mobile robot. More particularly, the present invention relates to a mobile robot of the type which stops at a charging station for automatic recharging when power remaining in the battery drops during self-controlled operation, and which departs from the charging station to resume normal operation at the end of the charging, and to a charging mechanism for charging the battery in the mobile robot.

2. Description of the Related Art

The term robot is said to be derived from Slavic word Robota (slave machine). In Japan, robots started to be widely used from the 1960s, and most of the robots were then industrial robots such as multiarticulate robot arms (manipulators) and conveyance robots for automating a production line in a plant or for use in an unmanned plant.

Research and development have advanced in moving (ambulatory) robots that use feet in walking and stable walk control for the mobile robots, such as pet-type or toy robots which imitate the living mechanisms and the behavior of four-footed animals such as the dog and the cat, and human-type robots which imitate the living mechanism and the behavior of human beings or apes. Expectations of commercializing these robots are currently mounting. The ambulatory robot is unstable and presents more difficulty in posture control and ambulation control than crawling robots. However, the ambulatory robot is excellent in that the ambulatory robot is flexible in walking and running, for instance, going up and down the stairs, and striding over an obstacle.

An installed robot, such as a robot arm, which is firmly planted at a particular location, is used for the assembling and selection of parts in a limited and local work space only. In contrast, the work space of the mobile robot is not limited. The mobile robot moves along a track or freely on a non-tracked area, performing any predetermined job. The mobile robot thus provides various services, instead of the human beings, the dogs, and other living things.

Humanoid robots coexist under the living environments of human beings, and perform a diversity of simple, risky and difficult jobs involved in the industrial and production activity of the human beings. For instance, the humanoid robots are expected to play an important role in various activities, such as maintenance work in nuclear power plants, thermoelectric power plants, and petrochemical plants, conveyance and assembly operation of parts in production plants, cleaning operations on high-rise buildings, and rescue activities in the site of a fire. The humanoid robot moves around or over an obstacle using the two feet thereof, reaching the site of activity in a self-controlled way, and performs a job exactly as instructed.

The mobile robots for entertainment imitating the dog or the cat, namely toy robots, have the feature of living together in a close relationship, rather than assisting the human beings in difficult jobs. The toy robots are easy to handle, compared with real animals, and offers sophisticated functions, compared with conventional toys.

Conventional toy machines offer fixed interactive relationship with a user operation, and cannot be modified according to the user's preference. As a result, the user may grow tired of the toy that simply repeats the same operation. In contrast, although the toy robot performs the operation in accordance with time-series action model, the toy robot modifies the time-series action model in response to an external stimulation such as a user operation. Specifically, by imparting a "learning effect" to the toy robot, the user enjoys preferable action patterns of which the user is free from being tired.

The toy robot may be programmed to dynamically respond to the user action as an owner, for instance, "praising", "playing with", "petting", "stroking", "chastising", or "beating". For instance, the toy robot may respond by "being pleased", "fawning on", "pouting", "chastising", "barking", or "wagging". The user thus enjoys an education simulation of the toy robot. The toy robot bipedally or quadrupedally walks within a room at home as a non-tracked work space, moving around or over an obstacle, freely and automatically in a self-controlled manner.

The above-discussed robots are motorized mechanical devices, thereby needing power feeding thereto.

Electric power is supplied from a utility AC supply through a power cable to a robot fixed at a particular location, such as the already-discussed robot arm, or to a robot that moves within a limited radius of action or along a limited action pattern.

It is impossible to feed power to the mobile robot moving around in a self-controlled fashion from the utility AC power supply, because the power cable limits the radius of action of the mobile robot. Self-propelled driving using a battery is a logical choice for the mobile robot. The battery-driven mobile robot runs in a diversity of work spaces, such as a living area of human beings, without any physical limitation such as the location of a wall outlet or the length of power cable.

The battery-driven robot needs battery charging, however. Although the mobile robot is used as an automatic device, a charging operation is an issue that needs to be addressed to construct a fully automatic device. The battery replacement for charging or the connection of a power connector are troublesome to the user.

A "charging station" has been introduced to perform the battery charging of the mobile robot in a reliable and fully automatic fashion. The charging station provides space dedicated to the battery charging of the mobile robot.

When the robot detects a drop in the power remaining in the battery during the self-propelled and self-controlled operation, the robot suspends the operation thereof, and automatically returns to and stops at the charging station. The charging station establishes electrical connection between the robot and the a power supply thereof, thereby supplying power to the battery of the robot. When the battery is fully charged or recovers the power thereof to a predetermined level, the electrical connection to the power supply is disconnected. The mobile robot departs from the charging station, and resumes the operation thereof that was once suspended.

With a plurality of charging stations arranged within a work space, the mobile robot receives power supplying from the charging station closest thereto. The mobile robot thus moves from station to station for charging, thereby expanding the radius of action thereof. On the other hand, one single charging station may be shared by a plurality of mobile robots. The charging function of the robot may partly be transferred to the charging station, and the required specifications of the robot itself may be made less severe, and the weight and cost of the mobile robot are reduced.

To smoothly and automatically put the mobile robot into a charging operation with the charging station in the middle of a job, the mobile robot needs to be guided into the charging station (or the mobile robot searches for the location of the charging station), while detecting the position thereof and controlling itself for accurate and reliable electrical connection with the power supply.

The mobile robot may be relatively easily set into the charging station if the robot (such as a conveyance robot) moves only along a predetermined fixed track. The charging station is arranged in the midway of the normal track, and the mobile robot comes to the charging station in one of the predefined steps, and performs the charging operation, practically without any interruption of the job.

Because of its freedom in motion, the robot, which is allowed to freely walk in a self-controlled manner, such as a humanoid robot or a toy robot, is associated with the difficulty of the position detection and alignment of the robot when the robot is set into the charging station.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a charging mechanism for a mobile robot which is battery-driven in a self-controlled fashion.

It is another object of the present invention to provide an excellent charging mechanism for a mobile robot which is battery-driven and freely and tracklessly moves within a work space.

It is yet another object of the present invention to provide an excellent charging mechanism which performs an charging operation using a charging station to charge the mobile robot which is battery-driven and freely and tracklessly moves within a work space.

It is yet another object of the present invention to provide an excellent charging mechanism which accurately and reliably establishes an electrical connection between a charging station and a mobile robot which stops at the charging station for a charging operation there.

In a first aspect of the present invention, a charging system for a mobile robot includes the mobile robot that is battery-driven and moves in a self-controlled way within a work space, and a charging station for accommodating the mobile robot for a battery charging operation. The charging system includes visible recognition data arranged in a predetermined location of the charging station, an image pickup unit mounted on the mobile robot, a calculating unit for calculating a range and a bearing from the mobile robot to the charging station, based on an image picked up by the image pickup unit, and a searching unit for causing the mobile robot to search for the charging station, based on the calculation result provided by the calculating unit.

In accordance with the first aspect, the mobile robot searches for the charging station based on the image picked up by a camera, with the visible recognition data arranged on the predetermined location on the charging station, as a target. The charging operation of the mobile robot moving on a non-tracked area is thus automated.

A communication unit for performing data exchange between the mobile robot and the charging station may be arranged. The communication unit may use any of interface protocols such as the RS-232C, IEEE1284, USB, i-Link, IrDA. The communication unit may be used for a guiding operation (for accurate alignment) when the mobile robot is received into the charging operation, or to notify of the start and end of charging.

The visible recognition data may be a print medium glued onto the surface of the charging station. A plurality of print media may be glued onto the surface of a three-dimensional object, such as a cylinder, a quadratic prism, or a sphere. In this way, the mobile robot detects the visible recognition data from a plurality of directions, and thus approaches to the charging station from various directions.

The visible recognition data may be displayed on a screen of a display unit. The visible recognition data is dynamically used in a manner that prevents the visible recognition data from being merged into the environment of the workspace. The visible recognition may be changed in response to a range from the mobile robot.

The visible recognition data may be a combination of colors and patterns. The visible recognition data may be a two-dimensional bar code or other visible marks.

By arranging the visible recognition data on an elevated portion of the charging station, the mobile robot detects the charging station from a far distance.

At least one of the charging station and the mobile robot may include an indicator indicating the condition of a battery, such as "Now charging", "Charging complete (with a battery fully charged)", or "Abnormal charging".

The charging station further includes a transmitter that transmits at least one of light ray, infrared ray, sound wave, ultrasonic wave, radio wave, and magnetic field, and the mobile robot includes a receiver for receiving the wave transmitted from the transmitter. In such a case, the calculating unit calculates the range and the bearing from the mobile robot to the charging station, based on at least one of the image provided by the image pickup unit and data received by the receiver. The charging station is accurately and quickly searched for.

Preferably, the wave transmitted by the transmitter is easily discriminated and separated from other signals created within the work space.

The mobile robot may include a head unit which performs a scanning motion with respect to a torso unit, and at least one of the image pickup unit and the receiver is arranged on the head unit. The charging station is thus easily detected through the scanning motion.

The transmitter may transmit at least two signal waves, from among light ray, infrared ray, sound wave, ultrasonic wave, radio wave, and magnetic field, and the receiver may switch the received signal in response to the range between the charging station and the mobile robot. The robot searches for the charging station using a sound wave, having diffractive property, in a far range where obstacles are dispersedly present midway, and switches to light ray or infrared light ray, having rectilinear propagation property, for precise searching in a near range.

The transmitter may project a light ray through a slit, and may change the pattern of the slit depending on the direction of light projection. With this arrangement, the mobile robot approaches the charging station from a plurality of directions with the single transmitter.

The transmitter may transmit at least two signal waves that are different in output intensity and frequency component. When a high-frequency signal is transmitted at a high intensity while a low-frequency signal being transmitted at a low intensity, an area where the high-frequency component only is received is considered to be relatively far from the charging station. When the mobile robot enters an area where a low-frequency component is received, the receiver detects that the mobile robot is closer to the charging station.

The charging station may include a communication unit for exchanging data with a device other than the devices of the charging system. The communication unit is a network interface card (NIC), for instance, and an external host system may remote-control the charging station through a network.

The transmitter may be arranged external to the charging station. The charging station may be searched for using a GPS (Global Positioning System).

The mobile robot may be of the four-footed type which quadrupedally walks like a dog, and includes a power connector on the abdomen of the torso unit thereof, the charging station may include a concaved receptacle, and a power connector arranged on the inner bottom portion of the receptacle, and the receptacle may support the mobile robot in the lying down position thereof.

The charging station may include, on the wall thereof, color patterns painted in at least two colors, and the mobile robot may search for the charging station, based on the positional relationship of the color patterns in an image provided by the image pickup unit.

The mobile robot may be of the four-footed type which quadrupedally walks like a dog, and may include a power connector on the hip portion of the torso unit thereof, the charging station may include a receptacle with a bowl-shaped concave, and a generally semi-spherical projection on the generally central position of the bowl-shaped concave, and the receptacle may support the mobile robot in the sitting position thereof.

The mobile robot may be of the four-footed type which quadrupedally walks like a dog, and may include a power connector on the hip portion of the torso unit thereof, the charging station may include a receptacle with a bowl-shaped, rotationally symmetric concave, and a generally semi-spherical, rotationally symmetric projection on the generally central position of the bowl-shaped concave, and the receptacle may support the mobile robot in the sitting position thereof at any angle.

The charging operation metaphorically represents feeding the dog in the sitting position thereof, and is interesting in the entertainment point of view.

The mobile robot may have a tapered portion on at least one of a head unit, and shoulders and hip portions of a torso unit, and the charging station may includes a generally U-shaped structure having an inner wall which receives the tapered portion formed on the mobile robot. The charging station may include a generally U-shaped structure having an inner wall which receives the tapered portion formed on the mobile robot, and on the deepest inside position of the U-shaped structure, a lip having a connector arranged on the top surface thereof. Each terminal of the connector may extend inwardly deeply into the U-shaped structure.

The mobile robot may be ambulatory, and an electrode terminal may be arranged on the sole of at least one foot. The electrical connection is established in normal walking.

The charging system may include at least one electromagnet for generating a magnetic field that connects and disconnects the connector of the mobile robot to and from the connector of the charging station.

The charging station may include a drive mechanism for placing the mobile robot in an appropriate engagement position therewith. With this arrangement, the mobile robot needs no precise alignment mechanism, the required specifications of the robot is made less severe, and the weight and cost of the mobile robot are reduced.

The charging station may include a generally U-shaped structure that receives the mobile robot, and a grip unit for gripping the mobile robot within the U-shaped structure. The charging station may be used as a carrying case with the mobile robot gripped therewithin. The U-shaped structure of the charging station protects the mobile robot against impacts that may be applied thereon when in transit.

The mobile robot may be of the type that quadrupedally walks like a dog, and the charging station may have a kennel-like configuration, and at least one connector may be arranged on the inner wall of the charging station.

In a second aspect of the present invention, a method for searching for a charging station, based on a signal wave transmitted by a transmitter arranged external to the charging station in a charging system including a mobile robot that is battery-driven and moves in a self-controlled way within a work space, and the charging station for accommodating the mobile robot for a battery charging operation, includes the steps of teaching the position of the charging station based on the signal wave from the transmitter after the mobile robot has been once placed on the charging station, and searching for the charging station by calculating the range and bearing to the charging station, based on the signal wave from the transmitter, with the mobile robot at any position within the work space.

In a third aspect of the present invention, a method for searching for a charging station, based on a signal wave transmitted by a transmitter arranged external to the charging station in a charging system including a mobile robot that is battery-driven and moves in a self-controlled way within a work space, and the charging station for accommodating the mobile robot for a battery charging operation, includes the steps of storing beforehand, in a memory of the mobile robot, the position information of the charging station with respect to a reference position set in accordance with the position of the transmitter, and searching for the charging station by calculating the position of the mobile robot with respect to the reference position, based on the signal wave from the transmitter with the mobile robot at any position within the work space, and reading the position information from the memory to calculate the range and the bearing to the charging station.

In a fourth aspect of the present invention, a method for searching for a charging station, based on a signal wave transmitted by a transmitter arranged external to the charging station in a charging system including a mobile robot that is battery-driven and moves in a self-controlled way within a work space, and the charging station for accommodating the mobile robot for a battery charging operation, includes the calculating step in which the mobile robot calculates the position thereof with respect to the reference position set in accordance with the position of the transmitter, based on the signal wave from the transmitter, the calculating step in which the charging station calculates the position of thereof with respect to the reference position, based on the signal wave from the transmitter, the communicating step in which the charging station communicates the position information thereof to the mobile robot, and the searching step in which the mobile robot searches for the charging station by calculating the range and bearing to the charging station through relative relationship between the positional information.

In a fifth aspect of the present invention, a mobile robot being ambulatory and having at least a torso unit and at least two foot units, includes an electrode terminal for power feeding, at the end of at least one of the two foot units. With the arrangement of the mobile robot, the electrical connection between electrodes is established in normal walking.

In a sixth aspect of the present invention, a mobile robot being ambulatory and having at least a torso unit and at least two foot units, includes an electrode terminal for power feeding, on one of the abdomen of the torso unit and the back of the torso unit.

In a seventh aspect of the present invention, a mobile robot being ambulatory and having at least a torso unit and at least two foot units, includes an electrode terminal for power feeding, at the end of the tail. With this arrangement, the electrical connection between electrodes is established by a charming action such as the wagging of the tail.

In an eighth aspect of the present invention, a connector having a generally semi-spherical projection, is cut into at least a tip thereof and one frustohemispherical slice, each serving as a connection terminal. The tip of the generally semi-spherical projection terminal may serve as a signal line, and the frustohemispherical terminal may serve as a power line. With this arrangement, an erratic connection between connectors is duly prevented.

In a ninth aspect of the present invention, an electrical connection structure performs electrical connection with connectors mutually in contact, wherein one connector is probe-like, and the other connector is mesh-like, and wherein the electrical connection is established with the probe-like connector is inserted into the mesh-like connector at any position. The probe-like connector may have a plurality of terminals arranged along the longitudinal direction thereof, and the mesh-like connector may have a plurality of layers.

In a tenth aspect of the present invention, and electrical connection structure performs electrical connection with connectors mutually in contact, wherein the electrical connection structure includes at least one electromagnet which connects and disconnects one connector to and from the other connector.

These and other objects, features and advantages will be readily understood from the following detailed description when read in connection with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external perspective view showing a mobile robot 1 of the present invention that quadrupedally walks;

FIG. 2 diagrammatically shows the electrical and control system of the mobile robot 1;

FIG. 3 shows the construction of a control unit 20 in detail;

FIG. 4 is a functional block diagram diagrammatically showing a work space which accommodates a charging station 80 and the mobile robot 1;

FIG. 5 diagrammatically shows a work space which accommodates the charging station 80, mobile robot 1, and external transmitter 90;

FIG. 6 is a flow diagram showing the process of a charging operation performed by the mobile robot 1 of the present invention;

FIG. 7 is a top view of the charging station 80-1 of a first embodiment of the present invention;

FIG. 8 is a sectional view of the charging station 80-1 of the first embodiment of the present invention;

FIG. 9 is a perspective view of the charging station 80-1 of the first embodiment of the present invention;

FIG. 10 is a perspective view of the charging station 80-2 of a second embodiment of the present invention;

FIG. 11 is a sectional view of the charging station 80-2 of the second embodiment of the present invention;

FIG. 12 is an enlarged perspective view of an electrical contact 82-2 in the charging station 80-2 of the second embodiment of the present invention;

FIG. 13 is an external view of a mobile robot 1-3 and a charging station 80-3 in accordance with a third embodiment of the present invention;

FIG. 14 shows the construction of an electrical connection in the charging station 80-3 of the third embodiment of the present invention;

FIG. 15 is an enlarged view showing only the electrical connection of the charging station 80-3;

FIG. 16 is a top view of a mobile robot 1-3 placed into the charging station 80-3;

FIG. 17 is a side view of the mechanism of an electrical connection, namely, a foot unit 6 with a connection terminal arranged on the tip thereof;

FIG. 18 is a bottom view of the mechanism of an electrical connection, namely, a foot unit 6 with a connection terminal arranged on the tip thereof;

FIG. 19 shows the mechanism of an electrical connection of in accordance with a fifth embodiment of the present invention;

FIG. 20 shows the mechanism of the electrical connection of in accordance with the fifth embodiment of the present invention;

FIG. 21 is a side view of a mobile robot 1-6 of a sixth embodiment of the present invention;

FIG. 22 is a bottom view of the mobile robot 1-6 of the sixth embodiment of the present invention;

FIG. 23 is a side view of a charging station 80-6 of a sixth embodiment with the internal construction thereof revealed;

FIG. 24 shows a modification of the charging station 80-6 of the sixth embodiment;

FIG. 25 shows a charging station 80-7 of a seventh embodiment of the present invention;

FIG. 26 shows the charging station 80-7 of the seventh embodiment of the present invention;

FIG. 27 is an external perspective view of a charging station 80-8 in accordance with an eighth embodiment of the present invention;

FIG. 28 is an external perspective view of a charging station 80-8' of a modification of the eighth embodiment;

FIG. 29 is an external perspective view of a charging station 80-9 in accordance with a ninth embodiment of the present invention;

FIG. 30 is an external view of a charging station 80-10 in accordance with a tenth embodiment of the present invention;

FIG. 31 shows a mechanism for engaging connectors in the charging station 80-10 of the tenth embodiment of the present invention;

FIG. 32 shows the connection mechanism of connectors in a modification of the tenth embodiment of the present invention;

FIG. 33 is an external perspective view showing a charging station 80-11 of an eleventh embodiment of the present invention;

FIG. 34 shows a connector-mating method in the eleventh embodiment of the present invention;

FIG. 35 shows another connector-mating method in the eleventh embodiment of the present invention;

FIG. 36 shows a connector 13-11 arranged on the tip of a tail 4;

FIG. 37 shows the internal construction of a kennel forming a charging station 80-11' in a modification of the eleventh embodiment;

FIG. 38 diagrammatically shows the layout of a cyber code; and

FIG. 39 shows an electrical connection between a charging station 80-12 and a mobile robot 1-12 in accordance with a twelfth embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention covers a charging mechanism which performs a charging operation using a charging station to a mobile robot, particularly, a battery-driven mobile robot that freely and tracklessly moves within a work space. The present invention may also be implemented in a mobile robot of the type which moves along a fixed track only.

In the discussion that follows, a quadrupedally walking robot is described. The present invention is not limited to this robot, and is implemented in ambulatory robots walking using two feet, four feet, and six feet, or robots having a crawling mechanism for locomotion.

The embodiments of the present invention are now discussed, referring to the drawings.

FIG. 1 is an external perspective showing a quadrupedally walking robot of the present invention. As shown, the mobile robot 1 is a multiarticulate robot that models the shape and construction of an animal having four limbs. The mobile robot 1 of this embodiment is a toy robot that is designed imitating the shape and construction of the dog, which is a typical pet of human beings. The mobile robot 1 expresses reactions in response to the action of a user in a way coexistent in the living environment of the human beings.

The mobile robot 1 includes a torso unit 2, a head unit 3, a tail 4, and four limbs, namely, foot units 6A-6D.

The head unit 3 is connected to the front end of the torso unit 2 through a neck joint 5 that has freedoms about the axes of roll, pitch and yaw (as shown). The head unit 3 includes a CCD (Charge-Coupled Device) camera 15 corresponding to the "eye" of the dog, a microphone 16 corresponding to the "ear" of the dog, a loudspeaker 17 corresponding to the "mouth" of the dog, and a touch sensor 18 corresponding to the touch of the dog. Optionally, more sensors for the five senses may be included.

The tail 4 is connected to the rear end of the torso unit 2 via a tail joint 8 having freedoms about the roll axis and the pitch axis, in a manner such that the tail 4 is curved upward to the end thereof or freely wags.

Foot units 6A and 6B are front feet, and foot units 6C and 6D are hind feet. The foot units 6A-6D are respectively composed of thighs 9A-9D and heels 10A-10D, and are respectively connected to the torso unit 2 on the side walls at the front and the back thereof. The thighs 9A-9D are connected to the torso unit 2 through shoulder and hip joints 11A-11D having freedom about each of the roll and pitch axes. The thighs 9A-9D are respectively connected to the heels 10A-10D via knee joints 12A-12D, each having freedom about the pitch axis.

The freedom of motion of the mobile robot 1 is actually provided by the rotation of the motor arranged at each axis (not shown). The number of degrees of freedom in the mobile robot 1 is not limited to any particular number and does not limit the scope of the present invention.

Referring to FIG. 2, the electrical and control system of the mobile robot 1 is shown. As shown, the mobile robot 1 includes a control unit 20 for generally controlling the operation of the mobile robot 1 and for processing data, an input/output unit 40, a driver unit 50, and a power supply unit 60. Theses units are now discussed.

The input/output unit 40 includes, as input devices, a variety of sensors for the five senses, such as the CCD camera 15 serving as the eye of the mobile robot 1, the microphone 16 serving as the ear, and the touch sensor 18 serving as the touch. The input/output unit 40 also includes, as an output device, the loudspeaker 17 serving as the mouth, and other devices, other than mechanical motion units such as foot units.

With the CCD camera 15, the mobile robot 1 recognizes the shape and color of any object present in the workspace. Besides the vision means such as the camera, the mobile robot 1 may also be equipped with receivers for receiving transmitted waves such as infrared light ray, sound wave, ultrasonic wave, radio wave. In this case, in response to the outputs of the sensors for receiving the waves, the mobile robot 1 can calculate the range and bearing to the source of the waves (as will be discussed later).

The driver unit 50 is a functional module for mechanically driving the mobile robot 1 in response to a predetermined action pattern commanded by the control unit 20, and is composed of blocks arranged at the neck joint 5, the tail joint 8, the shoulder and hip joints 11A-11D, the knee joints 12A-12D about the roll, pitch and yaw axes. Since the mobile robot 1 has n degrees of freedom at each joint as shown, the driver unit 50 thus includes n blocks, each including a motor 51 for driving a respective mechanical unit about a predetermined axis, an encoder 52 for detecting the angle of rotation of the motor 51, and a driver 53 for adaptively controlling the angle and speed of rotation of the motor 51 based on the output from the encoder 52.

The power supply unit 60 is a functional module for feeding power to each electrical circuit in the mobile robot 1. The mobile robot 1 of the present invention is a battery-driven and self-controlled robot, and the power supply unit 60 includes a rechargeable battery 61, and a charge/discharge controller 62 for controlling the charge/discharge state of the rechargeable battery 61.

The rechargeable battery 61 is a battery pack in which a plurality of lithium ion battery cells is packaged.

The charge/discharge controller 62 detects the power remaining in the rechargeable battery 61 by measuring the voltage across the terminals of the rechargeable battery 61, the charging and discharging currents of the rechargeable battery 61, and the ambient temperature of the rechargeable battery 61. The charge/discharge controller 62 thus determines the start time and stop time of the charging operation. The start time and stop time of the charging operation determined by the charge/discharge controller 62 are reported to the control unit 20, and serve as triggers for starting and ending the charging operation by the mobile robot 1. The charging operation will be discussed later.

The control unit 20 is the "brain" of the mobile robot 1, and is mounted in the head unit 3 of the mobile robot 1, for instance.

Referring to FIG. 3, the control unit 20 is illustrated in more detail. As shown, the control unit 20 includes a CPU (Central Processing Unit) 21 as a main controller, connected to memories and peripheral components and devices via buses. Devices on a bus 27 are assigned unique addresses (memory address or I/O addresses), and the CPU 21 can communicate with a particular device on the bus 27 by designating a corresponding address.

A RAM (Random Access Memory) 22 is a non-volatile rewritable memory such as DRAM (Dynamic RAM), and stores program codes to be executed by the CPU 21, and temporarily stores work data.

A ROM (Read Only Memory) 23 is a memory dedicated to permanently storing programs and data. The program codes stored in the ROM 23 include a self-diagnosis test program that is executed at the power on of the mobile robot 1, and control programs for defining the action of the mobile robot 1. The control programs include a "sensor output processing program" for processing sensor outputs from the camera 15 and the microphone 16, an "action command program" for generating an action pattern of the mobile robot 1 based on a "time-series model".sup./*/, and a "drive control program" for controlling the motors and the sound output from the loudspeaker 17 in accordance with the generated action pattern. Besides normal walking and running, the generated action patterns may include charming actions such as "shaking", "waiting", "sitting", and the bark or cry of the dog such as "bowwow".

.sup./*/ Time-series Model

The techniques of generating the action pattern of a mechanical apparatus such as a robot in accordance with a time-series model, and of updating the time-series model by learning an external stimulation are disclosed in Japanese Unexamined Patent Application Publication No. 11-2150 assigned to the assignee of this invention. Japanese Unexamined Patent Application Publication No. 11-129275, also assigned to the assignee of this invention, discloses a "robotic apparatus" which has an emotion instinct model based on an action, and updates the emotion instinct model in response to input information. Japanese Unexamined Patent Application Publication No. 11-129279 discloses a "robotic apparatus" that creates an action in accordance with a variety of action models such as an emotion model, an instinct model, a learning model, and a growth model.

A non-volatile memory 24 is an EEPROM (Electrically Erasable and Programmable ROM), and stores data to be successively updated, in a non-volatile fashion. The data to be successively updated is the time-series model that defines the action pattern of the mobile robot 1.

Through the sensors, the mobile robot 1 receives the actions by the user as the owner, such as "praising", "playing with", "petting", "stroking", "chastising", or "beating", as stimulations, and then expresses its emotions and feelings in accordance with the time-series model stored in the non-volatile memory 24. For instance, the mobile robot 1 responds by the reactions such as "being pleased", "fawning on", "pouting", "chastising", "barking", or "wagging". A learning effect is also imparted to the mobile robot 1 to successively update the time-series model stored in the non-volatile memory 24 in response to the stimulation input to the sensors. Through the learning effect, the action pattern of the mobile robot 1 is varied. The mobile robot 1 thus adaptively reacts in a manner that keeps the user from being tired of and is consistent with the user's own preference. The user thus enjoys an education program in a game playing manner.

An interface 25 connects the control unit 20 with devices external to the control unit 20 for data exchanging therebetween. For instance, the interface 25 exchanges data with the camera 15, microphone 16, and loudspeaker 17. The interface 25 also exchanges data and commands with the drivers 53-1, . . . , in the driver unit 50. Furthermore, the interface 25 exchanges the charging start time and charging stop time signals with the power supply unit 60.

The interface 25 includes general-purpose interfaces for communication with computer peripheral devices, such as an RS (Recommended Standard)-232C serial interface, an IEEE (Institute of Electrical and Electronics Engineers) 1284 parallel interface, a USB (Universal Serial Bus) interface, an i-Link (IEEE 1394) interface, and an SCSI (Small Computer System Interface). The interface 25 thus exchanges programs and data with an external device, such as the charging station 80 (to be discussed later).

The interface 25 may include an infrared communication (IrDA) interface, thereby performing wireless communication with an external device, such as the charging station 80. A transceiver for the infrared communication is preferably arranged on an end portion of the mobile robot 1, i.e., the head unit 3 or tail 4, from the sensitivity standpoint.

The control unit 20 includes a network interface card (NIC) 26, and communicates with an external computer system for data exchange via a LAN (Local Area Network) or the Internet, and may remote-control the mobile robot 1 using the resources of the remote computer. The time-series model to be stored in the non-volatile memory 24 is supplied to the mobile robot 1 via the network.

As discussed in the Description of the Related Art, a self-controlled and self-driven robot, such as the mobile robot 1 of this embodiment, is battery charged using the charging station. The charging station is a docking station that docks the mobile robot 1 to charge the battery thereof. Such a charging station has widely been used in the industrial fields of robots as a method for reliably and fully automating battery charging of mobile robots.

Upon detecting a drop in the power remaining in the rechargeable battery 61 in the middle of self-driven and self-controlled job, the mobile robot 1 stops the job and comes to the charging station 80. The mobile robot 1 establishes electrical connection with the power supply in the charging station 80, thereby receiving power for the rechargeable battery 61. When the rechargeable battery 61 is fully charged or recovers the voltage thereof to a predetermined level, the mobile robot 1 electrically disconnects itself from the charging station 80, departs from the charging station 80, and resumes the job once suspended.

The external appearance of the charging station 80 is not limited to any particular one. When the toy robot 1 takes the external appearance of a dog as shown in FIG. 1, the charging station may be configured to imitate a bed or kennel for the dog. With this arrangement, the kennel is metaphorically represented by the charging station at which the mobile robot 1 stops for recharging, and increases the fun to play with the mobile robot 1 besides normal operation of the mobile robot 1.

When a plurality of charging stations are arranged within the work space, the mobile robot 1 is recharged at a charging station closest thereto. The mobile robot 1 thus travels between the charging stations, expanding the radius of action thereof. A single charging station is shared among a plurality of mobile robots, and the number of the charging stations is reduced. The charging function of the robot may partly be transferred to the charging station, and the required specifications of the robot itself may be made less severe, and the weight and cost of the mobile robot are reduced.

FIG. 4 is a functional block diagram diagrammatically showing a work space in which the charging station 80 and the mobile robot 1 are arranged.

The charging station 80 of this embodiment includes display unit 82, transmitter 83, proximity and connection detector 84, interface 85, power supply control unit 86, and interface