EP4665544A1

EP4665544A1 - Control system, control method, and storage medium

Info

Publication number: EP4665544A1
Application number: EP23836943.3A
Authority: EP
Inventors: Yoshihiro Okumatsu; Hiroshi Bito; Akihito Goto; Kazutomo MISAO; Takemitsu Mori
Original assignee: Toyota Motor Corp
Current assignee: Toyota Motor Corp
Priority date: 2023-02-17
Filing date: 2023-12-13
Publication date: 2025-12-24
Also published as: JP7845221B2; JP2024117307A; CN120641247A; WO2024170951A1

Abstract

A service robot includes a backdrivable robot arm, a robot body that supports the robot arm, a mobile carriage that is provided at a lower portion of the robot body, and a control unit that controls the robot arm and the mobile carriage. The control unit is configured to execute a collision relaxation control in response to action of external force caused by contact with a peripheral object on the robot arm during movement of the service robot using the mobile carriage.

Description

CONTROL SYSTEM, CONTROL METHOD, AND STORAGE MEDIUM

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The present disclosure relates to a control system, a control method, and a storage medium.

2. Description of Related Art

[0002] Japanese Unexamined Patent Application Publication No. 2022-032166 (JP 2022-032166 A) discloses an autonomous mobile object. In the autonomous mobile object, contact sensors are provided on a plurality of bumpers that is disposed so as to surround a periphery of a mobile carriage. The autonomous mobile object is configured to detect contact with a peripheral object based on signals that are output from the contact sensors.

SUMMARY OF THE INVENTION

[0003] In the configuration in JP 2022-032166 A, it is necessary to keep the movement speed of the autonomous mobile object at a low speed, in order not to cause damage to a peripheral object when the bumpers collide with the peripheral object.

[0004] The present disclosure provides a technology for realizing the high-speed movement of the autonomous mobile body.

[0005] A first aspect of the present disclosure provides a control system including: an autonomous mobile object including a backdrivable robot arm, a robot body that supports the robot arm, and a mobile carriage that is provided at a lower portion of the robot body; and a control unit configured to execute a collision relaxation control in response to action of external force on the robot arm during movement of the autonomous mobile object using the mobile carriage, the external force being caused by contact with a peripheral object. With the above configuration, the high-speed movement of the autonomous mobile object is realized.

The collision relaxation control may be a control to change the movement direction of the autonomous mobile object.

The collision relaxation control may be a control to decrease the movement speed of the autonomous mobile object.

The control unit may be configured to control the robot arm or the mobile carriage such that the robot arm is positioned forward of the robot body in the movement direction of the autonomous mobile object during the movement of the autonomous mobile object using the mobile carriage. With the above configuration, it is possible to efficiently detect the contact between the autonomous mobile object and the peripheral object.

The control unit may be configured to control the robot arm such that the robot arm protrudes forward of the mobile carriage in the movement direction of the autonomous mobile object in planar view. With the above configuration, it is possible to efficiently detect the contact between the autonomous mobile object and the peripheral object.

The control unit may be configured to have a plurality of sensing modes including at least a first sensing mode and a second sensing mode, to select one of the plurality of sensing modes, and to control the attitude of the robot arm based on the selected sensing mode, the first sensing mode being a sensing mode in which the attitude of the robot arm is a first attitude, the second sensing mode being a sensing mode in which the attitude of the robot arm is a second attitude different from the first attitude. With the above configuration, it is possible to realize different sensing ranges.

The autonomous mobile object may further include a peripheral environment monitoring unit configured to monitor a peripheral environment, and the control unit may be configured to select one of the plurality of sensing modes based on the peripheral environment. With the above configuration, it is possible to select an optimal sensing mode depending on the peripheral environment.

In the first attitude, the height position of an end effector of the robot arm may be a first height position, and in the second attitude, the height position of the end effector of the robot arm may be a second height position different from the first height position. With the above configuration, it is possible to perform sensing in ranges that are different in the vertical direction.

The control unit may be configured to swing the robot arm in a fan-like manner during the movement of the autonomous mobile object using the mobile carriage. With the above configuration, a wide-range sensing is realized.

The robot arm may include at least two links, and a joint that couples the at least two links. The autonomous mobile object may further include an actuator configured to drive the joint, the actuator being provided in the robot body, and a dynamic power transmission mechanism configured to transmit dynamic power generated by the actuator, to the joint.

The dynamic power transmission mechanism may include a belt or a wire. With the above configuration, the weight reduction of the robot arm is realized.

The control unit may be configured to perform an impedance control of the robot arm. With the above configuration, the backdrivable robot arm can be realized by a simple control.

The control system may further include a contact sensor configured to detect that the peripheral object has come into contact with the mobile carriage during the movement of the autonomous mobile object using the mobile carriage. The control unit may be configured to stop movement of the autonomous mobile object when the contact sensor has detected that the peripheral object has come into contact with the mobile carriage. With the above configuration, it is possible to stop the movement of the autonomous mobile object when the mobile carriage has come into contact with the peripheral object.

A second aspect of the present disclosure provides a control method for an autonomous mobile object, the autonomous mobile object including a backdrivable robot arm, a robot body that supports the robot arm, and a mobile carriage that is provided at a lower portion of the robot body. The control method includes: moving the autonomous mobile object using the mobile carriage; and executing a collision relaxation control in response to action of external force on the robot arm during movement of the autonomous mobile object using the mobile carriage, the external force being caused by contact with a peripheral object. With the above method, the high-speed movement of the autonomous mobile object is realized.

A non-transitory storage medium storing instructions that are executable by one or more processors of a computer and that cause the one or more processors to perform the above control method is provided.

[0006] With the present disclosure, the high-speed movement of the autonomous mobile object is realized.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like signs denote like elements, and wherein:

FIG. 1 is a perspective view of a service robot;

FIG. 2 is a lateral view of a robot arm;

FIG. 3 is a lateral view of the robot arm;

FIG. 4 is a functional block diagram of the service robot;

FIG. 5 is an explanatory diagram for a first sensing mode;

FIG. 6 is an explanatory diagram for a second sensing mode;

FIG. 7 is an explanatory diagram for a third sensing mode;

FIG. 8 is an explanatory diagram for a fourth sensing mode;

FIG. 9 is a control flow for the service robot;

FIG. 10 is a plan view of a service robot in a first modification;

FIG. 11 is a control flow for a service robot in a second modification;

FIG. 12 is a schematic view of a control system in a third modification;

FIG. 13 A is an explanatory diagram for backdrivability;

FIG. 13B is an explanatory diagram for backdrivability; and

FIG. 13C is an explanatory diagram for backdrivability.

DETAILED DESCRIPTION OF EMBODIMENTS

[0008] An embodiment of the present disclosure will be described below with reference to FIG. 1 to FIG. 9.

[0009] FIG. 1 shows an autonomous mobile service robot 1. The service robot 1 is a specific example of the autonomous mobile object. For example, the service robot 1 provides various services in a medical facility, a nursing facility or other facilities. The various services include a carrying service for carrying an article, a patrol service for patrolling in the facility, and other services. FIG. 1 shows a state where the service robot 1 is carrying a beverage container 2.

[0010] The service robot 1 includes a robot arm 3, a robot body 4, a mobile carriage 5 that is provided at a lower portion of the robot body 4, and a control unit 6 that controls the robot arm 3 and the mobile carriage 5.

[0011] In the embodiment, the robot arm 3 is configured as a multijoint type. Moreover, the robot arm 3 is configured as a so-called backdrivable robot arm. When the robot arm 3 is backdrivable, typically, the joint angle of the robot arm 3 changes when external force is applied to the robot arm 3. The external force does not include the external force due to gravitational acceleration, and means the external force caused by the contact with a peripheral object.

[0012] The definition of backdrivability is described in more detail in "Journal of the Robotics Society of Japan Vol. 31, No. 6, pp.548-551, 2013"

(https://www.jstage.jst.go.jp/article/jrsj/31/6/31_3 l_548/_pdf/-char/ja)

[0013] A phenomenon in which a drive system operates when the external force is applied to a joint of the robot or an output shaft of an actuator is referred to as backdrive. The backdrivability is a concept indicating "ease of backdrive". A human arm assumes a dangling state when the tension is released (when the muscle is relaxed). Such a high backdrivability can be easily realized by living creatures, but is quite difficult by robots under current circumstances.

[0014] Generally, a drive system including an electromagnetic motor and a speed reducer shown in FIG. 13A is assumed, and the backdrive is "a phenomenon in which the speed reducer and the motor rotate when external torque T is applied to the output shaft". In this case, one of most important factors that determine the backdrivability is the friction in the speed reducer, and therefore the definition is appropriate when a drive system with low friction is discussed from a standpoint of kinematics. Meanwhile, in robotics, the characteristic of the robot is often argued using the concept of the backdrivability. In that case, it is beneficial to interpret the backdrive in a broad sense, simply as "operating of an output link due to the external force".

[0015] When the backdrive is interpreted in a broad sense, there can be a variety of configurations, as the configuration of the drive system that realizes the backdrive. FIG. 13B shows an example in which the external force is detected by a torque sensor and the motor is driven based on a detection signal of the torque sensor. Thereby, the backdrive can be realized even in a drive system that includes speed reducer with high friction. Further, when information of an encoder shown by a dotted line in FIG. 13B is concurrently used, it is possible to realize various resistance forces that depend on rotation angle, speed, and acceleration. From a further expanded perspective, there is also a method in which a clutch and a brake are used for the output shaft as shown in FIG. 13C. When the clutch is turned off, a follower assumes a dangling state, and when the brake is used, the backdrive is not performed. When a viscous damper or an elastic body is used instead of the clutch, viscous resistance and compliance can be realized. The backdrive shown in FIG. 13B can be referred to as servo backdrive, and the backdrive shown in FIG. 13C can be referred to as mechanical backdrive.

[0016] In short, the "backdrivable" in a broad sense means that the joint angle of the robot arm 3 changes when the external force is applied to the robot arm 3. In the "backdrivable" in a narrow sense, the action of the external force on the robot arm 3 is detected in some way, for example, using the torque sensor or the encoder. The "backdrivable" in a narrow sense is configured such that the robot arm 3 is initiatively controlled based on the detection result and thereby the joint angle of the robot arm 3 is changed in response to the action of the external force on the robot arm 3. In the "backdrivable" in a narrow sense, for example, it is possible that the external force that enters the output shaft of the robot arm 3 is actively treated as a control command signal for the robot and thereby the friction in the drive system of the robot arm 3 is compensated.

[0017] Further, regardless of the types of the servo motor and the speed reducer that are included the robot arm 3, when infinite external force acts on the robot arm 3, the output shaft of the serve motor rotates more than slightly. Accordingly, the "backdrivable" in the embodiment can be defined also by the degree of the external force that can change the joint angle of the robot arm 3. That is, in the case where the joint angle of the robot arm 3 is changed due to the contact of the robot arm 3 with a moving object such as a walker and another mobile robot, it can be said that the robot arm 3 is backdrivable. Further, in the case where the joint angle of the robot arm 3 is changed due to the contact of the robot arm 3 with a stationary object such as a wall and furniture, it can be said that the robot arm 3 is backdrivable.

[0018] As described above, various techniques can be employed as the technique for realizing the backdrivability of the robot arm 3.

[0019] A first technique is to decrease the speed reduction ratio of a speed reduction mechanism that is provided for the output shaft of the actuator of the robot arm 3. This is because the most important factor that hinders the backdrivability of the robot arm 3 is the friction in the speed reduction mechanism and therefore the decrease in the friction is effective for the backdrivability.

[0020] A second technique is to use an electromagnetic clutch for the output shaft of the actuator of the robot arm 3. When the electromagnetic clutch is disengaged, a link that is driven by the actuator can be temporarily put into a dangling state.

[0021] A third technique is to perform an impedance control of the robot arm 3. The impedance control is to control the robot arm 3 such that the joint of the robot arm 3 behaves like a spring or a damper. The impedance control includes an impedance control that is performed using a torque sensor that directly detects the external force and an impedance control that is performed without using the torque sensor.

[0022] In the embodiment, as an example, the backdrivability of the robot arm 3 is realized by employing the third technique. However, the first technique or the second technique may be employed instead of the third technique.

[0023] The robot body 4 supports the robot arm 3 in a cantilever manner. The robot body 4 includes a robot base 10, a slide mechanism 11, an arm base 12, a lifting actuator 13, and a head 14. The robot base 10 has a rectangular parallelepiped shape that is long in the vertical direction. The slide mechanism 11 is provided on a front surface 10a of the robot base 10. The arm base 12 is supported by the slide mechanism 11, so as to be capable of going up and down, and is coupled to the robot arm 3. The lifting actuator 13 drives the arm base 12 such that the arm base 12 goes up and down along the slide mechanism 11. For example, the lifting actuator 13 moves up the arm base 12 along the slide mechanism 11, and thereby can move up the whole of the robot arm 3. Similarly, for example, the lifting actuator 13 moves down the arm base 12 along the slide mechanism 11, and thereby can move down the whole of the robot arm 3. Typically, the lifting actuator 13 is a servo motor. The dynamic power of the lifting actuator 13 is transmitted to the arm base 12 through an unillustrated endless belt. The head 14 is provided above the robot base 10. On the head 14, a camera 15 and a Light Detection And Ranging (Lidar) 16 are provided. The camera 15 and the Lidar 16 are used for acquiring a peripheral environment. The camera 15 is a specific example of an image sensor. The camera 15 outputs image data obtained by imaging the peripheral environment, to the control unit 6. The Lidar 16 is a specific example of a distance sensor. The Lidar 16 outputs three-dimensional point cloud data obtained by scanning the peripheral environment, to the control unit 6. As the distance sensor, a stereo camera or a pattern projection camera can be employed instead of the Lidar 16.

[0024] The mobile carriage 5 includes a carriage body 20 and a bumper 21. [0025] As an example, the carriage body 20 includes two driving wheels 22, one driven wheel 23, and two carriage motors 24 that drive the two driving wheels 22, respectively. The two carriage motors 24 drive the two driving wheels 22 at the same rotation speed in the same rotation direction, respectively, and thereby the service robot 1 moves forward or rearward. The two carriage motors 24 drive the two driving wheels 22 at different rotation speeds in the same rotation direction, respectively, and thereby the service robot 1 turns. The two carriage motors 24 drive the two driving wheels 22 in different rotation directions, respectively, and thereby the service robot 1 performs spin turning. The bumper 21 is a rigid body that is circularly provided on an outer circumference of the carriage body 20, and protects the carriage body 20 from the collision with the peripheral object. A bumper sensor 25 that detects the contact of the bumper 21 with the peripheral object is provided in the bumper 21. The bumper sensor 25 is a specific example of the contact sensor. Typically, the bumper sensor 25 is configured by an acceleration sensor or a strain gauge. However, the configuration of the bumper sensor 25 is not limited to this.

[0026] FIG. 2 shows a lateral view of the robot arm 3. The robot arm 3 in the embodiment employs a structure in which a human arm is simulated. That is, the robot arm 3 includes an upper arm link 30, a forearm link 31, a shoulder joint 32, an elbow joint 33, and a wrist joint 34. The upper arm link 30 is coupled to the arm base 12 through the shoulder joint 32, such that pitch turning and roll turning can be performed. The forearm link 31 is coupled to the upper arm link 30 through the elbow joint 33, such that pitch turning can be performed. A grip type end effector 35 is provided at a distal end of the forearm link 31. The end effector 35 is coupled to the forearm link 31 through the wrist joint 34, such that pitch turning can be performed.

[0027] The arm base 12 of the service robot 1 includes a shoulder joint actuator 40 that drives the shoulder joint 32, an elbow joint actuator 41 that drives the elbow joint 33, and a wrist joint actuator 42 that drives the wrist joint 34. That is, the shoulder joint actuator 40, the elbow joint actuator 41, and the wrist joint actuator 42 are provided in the arm base 12 of the service robot 1. Thereby, the weight reduction of the robot arm 3 is realized, for example, compared to a direct-drive type in which the elbow joint actuator 41 is provided on the elbow joint 33. Because of the weight reduction of the robot arm 3, it is possible to reduce the damage that is caused to the peripheral object when the robot arm 3 comes into contact with the peripheral object. In other words, by the weight reduction of the robot arm 3, it is possible to realize the backdrivability of the robot arm 3 at a high level.

[0028] Typically, each of the shoulder joint actuator 40, the elbow joint actuator 41, and the wrist joint actuator 42 is a servo motor. An output shaft of the shoulder joint actuator 40 is connected to a shoulder joint pulley 40b through a speed reduction mechanism 40a. Similarly, an output shaft of the elbow joint actuator 41 is connected to an elbow joint pulley 41b through a speed reduction mechanism 41a. Similarly, an output shaft of the wrist joint actuator 42 is connected to a wrist joint pulley 42b through a speed reduction mechanism 42a.

[0029] The shoulder joint pulley 40b is coupled to an upper arm link pulley 30a through an endless belt 30b. The upper arm link pulley 30a is provided in the shoulder joint 32 that is a pitch turning shaft of the upper arm link 30. The upper arm link pulley 30a is fixed so as to be incapable of rotating with respect to the upper arm link 30. Accordingly, the endless belt 30b transmits the dynamic power generated by the shoulder joint actuator 40, to the shoulder joint 32. The endless belt 30b is a specific example of the dynamic power transmission mechanism. An equivalent configuration is provided also for the roll turning of the upper arm link 30.

[0030] The elbow joint pulley 41b is coupled to a forearm link pulley 31a through an endless belt 3 lb. The forearm link pulley 3 la is provided in the elbow joint 33 that is a pitch turning shaft of the forearm link 31. The forearm link pulley 3 la is fixed so as to be incapable of rotating with respect to the forearm link 31. Accordingly, the endless belt 3 lb transmits the dynamic power generated by the elbow joint actuator 41, to the elbow joint 33. The endless belt 3 lb is a specific example of the dynamic power transmission mechanism.

[0031] The wrist joint pulley 42b is coupled to an end effector pulley 35a through two wires 35b. The end effector pulley 35a is provided in the wrist joint 34 that is a pitch turning shaft of the end effector 35. One end of each wire 35b is fixed to an outer circumference of the wrist joint pulley 42b, and the other end is fixed to an outer circumference of the end effector pulley 35 a. Accordingly, the two wires 35b transmit the dynamic power generated by the wrist joint actuator 42, to the wrist joint 34. The two wires 35b are a specific example of the dynamic power transmission mechanism.

[0032] The configuration of the dynamic power transmission mechanism is not limited to the above configuration, and may be a configuration shown in FIG. 3, for example. In the configuration shown in FIG. 3, a pinion gear 45 is provided on the output shaft of the elbow joint actuator 41 through the speed reduction mechanism 41a. A pinion gear 46 fixed so as to be incapable of rotating with respect to the forearm link 31 is provided in the elbow joint 33. The pinion gear 45 and the pinion gear 46 coordinate through a drive shaft 47. That is, a worm gear 48 that engages with the pinion gear 45 is provided at one end of the drive shaft 47, and a worm gear 49 that engages with the pinion gear 46 is provided at the other end. A universal joint 50 may be provided on the drive shaft 47, such that the drive shaft 47 can be bent at the shoulder joint 32.

[0033] Next, the electric configuration of the service robot 1 will be described with reference to FIG. 4.

[0034] The control unit 6 includes a central processing unit (CPU) 60, a random access memory (RAM) 61, a read only memory (ROM) 62, a hard disc drive (HDD) 63, and a communication interface 64. In the HDD 63, map data 65 about the service environment is stored. The CPU 60 reads and executes a control program stored in the HDD 63, and thereby, the control program causes hardware such as the CPU 60 to function as a destination setting unit 70, an own position estimation unit 71, a route generation unit 72, and an autonomous movement control unit 73.

[0035] The destination setting unit 70 sets the destination of the service robot 1 based on an external input through the communication interface 64.

[0036] The own position estimation unit 71 estimates the current position of the service robot 1 by collating the image data output from the camera 15 and the map data 65. As the own position estimation technique, typically, a particle filter is used, but the own position estimation technique is not limited to this.

[0037] The route generation unit 72 generates a route from the current position of the service robot 1 to the destination.

[0038] The autonomous movement control unit 73 controls the robot arm 3 and the mobile carriage 5. That is, the autonomous movement control unit 73 controls the mobile carriage 5 such that the service robot 1 moves along the route generated by the route generation unit 72. Further, in the embodiment, the autonomous movement control unit 73 is configured to detect the contact between the service robot 1 and the peripheral object during the movement of the service robot 1, using the robot arm 3. Therefore, as illustrated in FIG. 5 to FIG. 7, the autonomous movement control unit 73 controls the robot arm 3 or the mobile carriage 5 such that at least a part or the whole of the robot arm 3 is positioned forward of the robot body 4 in the movement direction of the service robot 1 during the movement of the service robot 1 using the mobile carriage 5. More specifically, the autonomous movement control unit 73 controls the robot arm 3 such that at least a part or the whole of the robot arm 3 protrudes forward of the mobile carriage 5 in the movement direction of the service robot 1 in planar view.

[0039] Back to FIG. 4, the autonomous movement control unit 73 has a plurality of sensing modes. The plurality of sensing modes includes a first sensing mode 80, a second sensing mode 81, a third sensing mode 82, and a fourth sensing mode 83. The autonomous movement control unit 73 selects one of the plurality of sensing modes, based on the image data output from the camera 15 and the three-dimensional point cloud data output from the Lidar 16, and controls the attitude of the robot arm 3 based on the selected sensing mode.

[0040] The first sensing mode 80 is a sensing mode for controlling the attitude of the robot arm 3 such that the end effector 35 of the robot arm 3 is positioned above an upper end 4a of the robot body 4 as shown in FIG. 5. The upper arm link 30 extends from the arm base 12 obliquely upward, and the forearm link 31 extends upward along the vertical direction. For example, in the case where a drone type delivery robot is flying in the service environment, there is a risk that the drone type delivery robot comes into contact with the head 14 of the service robot 1. Accordingly, in this case, it is necessary to protect the head 14 of the service robot 1. Therefore, the autonomous movement control unit 73 selects the first sensing mode 80, and controls the attitude of the robot arm 3 such that the attitude of the robot arm 3 becomes the attitude shown in FIG. 5 based on the first sensing mode 80. The attitude of the robot arm 3 shown in FIG. 5 is a specific example of the first attitude.

[0041] As shown in FIG. 5, in the first sensing mode 80, the height position of the end effector 35 is a first height position Hl . As described above, the first height position Hl is a position that is higher than the upper end 4a of the robot body 4. In the first sensing mode 80, the forearm link 31 extends in the vertical direction. Accordingly, a sensing range SRI when the first sensing mode 80 is selected is a range corresponding to the link length of the forearm link 31 in the vertical direction.

[0042] The second sensing mode 81 is a sensing mode for controlling the attitude of the robot arm 3 such that the end effector 35 of the robot arm 3 is positioned slightly below the upper end 4a of the robot body 4 as shown in FIG. 6. The upper arm link 30 extends from the arm base 12 obliquely downward, and the forearm link 31 extends upward along the vertical direction. For example, in the case where there are many walkers in the service environment, there is a risk that a walker comes into contact with the service robot 1. Accordingly, in this case, in order that the robot arm 3 does not come into contact with the head of the walker, the autonomous movement control unit 73 selects the second sensing mode 81, and controls the attitude of the robot arm 3 such that the attitude of the robot arm 3 becomes the attitude shown in FIG. 6 based on the second sensing mode 81. The attitude of the robot arm 3 shown in FIG. 6 is a specific example of the second attitude.

[0043] As shown in FIG. 6, in the second sensing mode 81, the height position of the end effector 35 is a second height position H2. The second height position H2 is a height position that is lower than the first height position Hl. As described above, the second height position H2 is a position that is slightly lower than the upper end 4a of the robot body 4. In the second sensing mode 81, the forearm link 31 extends in the vertical direction. Accordingly, a sensing range SR2 when the second sensing mode 81 is selected is a range corresponding to the link length of the forearm link 31 in the vertical direction.

[0044] The third sensing mode 82 is a sensing mode for controlling the attitude of the robot arm 3 such that the end effector 35 of the robot arm 3 is positioned near a floor surface F in the service environment as shown in FIG. 7. The upper arm link 30 extends from the arm base 12 obliquely downward, and the forearm link 31 extends downward along the vertical direction. For example, in the case where an autonomous cleaning robot is running in the service environment, there is a risk that the autonomous cleaning robot comes into contact with the mobile carriage 5 of the service robot 1. Accordingly, in this case, in order to decrease the frequency of the emergency stop of the service robot 1 due to the contact of the autonomous cleaning robot with the mobile carriage 5, the autonomous movement control unit 73 selects the third sensing mode 82, and controls the attitude of the robot arm 3 such that the attitude of the robot arm 3 becomes the attitude shown in FIG. 7 based on the third sensing mode 82.

[0045] As shown in FIG. 7, in the third sensing mode 82, the height position of the end effector 35 is a third height position H3. The third height position H3 is a height position that is lower than the first height position Hl and the second height position H2. As described above, the third height position H3 is a position near the floor surface F. In the third sensing mode 82, the forearm link 31 extends in the vertical direction. Accordingly, a sensing range SR3 when the third sensing mode 82 is selected is a range corresponding to the link length of the forearm link 31 in the vertical direction.

[0046] As shown in FIG. 5 to FIG. 7, the sensing range SRI in the first sensing mode 80, the sensing range SR2 in the second sensing mode 81, and the sensing range SR3 in the third sensing mode 82 are set so as to have different heights from each other. In this way, in the embodiment, it is possible to flexibly set a suitable sensing rage depending on the peripheral environment.

[0047] The fourth sensing mode 83 is a sensing mode for swinging the robot arm 3 right and left in a fan-like manner on the front surface side of the service robot 1 as shown in FIG. 8. In this way, the autonomous movement control unit 73 swings the robot arm 3. Thereby, it is possible to detect the contact with the peripheral object in a range that is wide as viewed in the movement direction of the service robot 1. In the example in FIG. 8, the autonomous movement control unit 73 swings the robot arm 3 below the arm base 12. However, instead of this, the autonomous movement control unit 73 may swing the robot arm 3 above the arm base 12.

[0048] The autonomous movement control unit 73 executes a collision relaxation control when the external force caused by the contact with the peripheral object acts on the robot arm 3 during the movement of the service robot 1 using the mobile carriage 5. Specifically, the autonomous movement control unit 73 can detect the above external force as external force torque, by monitoring current values of the shoulder joint actuator 40, the elbow joint actuator 41, and the wrist joint actuator 42. Instead of this, the autonomous movement control unit 73 may detect the action of the above external force, based on output values of encoders provided for the shoulder joint actuator 40, the elbow joint actuator 41, and the wrist joint actuator 42. In addition, a strain gauge may be attached to the upper arm link 30 or the forearm link 31, and the autonomous movement control unit 73 may detect the action of the above external force based on an output value of the strain gauge.

[0049] Typically, the above collision relaxation control is a control to decrease the movement speed of the service robot 1 or a control to change the movement direction of the service robot 1. The above collision relaxation control may be a control to change the movement direction of the service robot 1 while decreasing the movement speed of the service robot 1. In the embodiment, the collision relaxation control is the control to change the movement direction of the service robot 1.

[0050] Next, the operation of the service robot 1 will be described with reference to FIG. 9.

[0051] First, the destination setting unit 70 sets the destination (SI 00). Next, the own position estimation unit 71 estimates the current position of the service robot 1 (SI 10). Next, the route generation unit 72 generates the route from the current position of the service robot 1 to the destination (S120). Next, the autonomous movement control unit 73 acquires, as environment information, the image data output from the camera 15 and the three-dimensional point cloud data output from the Lidar 16 (S130). Next, the autonomous movement control unit 73 selects the sensing mode based on the environment information (S140). Specifically, in the case where the drone type delivery robot is detected based on the environment information, the autonomous movement control unit 73 selects the first sensing mode 80. In the case where the walker is detected based on the environment information, the autonomous movement control unit 73 selects the second sensing mode 81. In the case where the autonomous cleaning robot is detected based on the environment information, the autonomous movement control unit 73 selects the third sensing mode 82. In other cases, the autonomous movement control unit 73 selects the fourth sensing mode 83.

[0052] Next, the autonomous movement control unit 73 starts the autonomous movement along the route generated by the route generation unit 72, and controls the attitude of the robot arm 3 based on the selected sensing mode (SI 50). Next, the own position estimation unit 71 estimates the current position of the service robot 1 (SI 60). Next, the autonomous movement control unit 73 acquires, as the environment information, the image data output from the camera 15 and the three-dimensional point cloud data output from the Lidar 16 (SI 70). Next, the autonomous movement control unit 73 selects the sensing mode based on the environment information (SI 80). The autonomous movement control unit 73 may select the sensing mode, using a neutral network after learning that outputs the sensing mode when receiving the environment information. Next, in the case where the sensing mode selected in step SI 80 is different from the sensing mode that is currently being executed, the autonomous movement control unit 73 switches the sensing mode to be executed from now, to the sensing mode selected in step SI 80 (SI 90).

[0053] Next, the autonomous movement control unit 73 determines whether the external force caused by the contact with the peripheral object has acted on the robot arm 3 during the movement of the service robot 1 using the mobile carriage 5 (S200). In the case where the autonomous movement control unit 73 determines that the external force has acted, the autonomous movement control unit 73 causes the process to proceed to S210. On the other hand, in the case where the autonomous movement control unit 73 determines that the external force has not acted, the autonomous movement control unit 73 causes the process to proceed to S230.

[0054] Next, the autonomous movement control unit 73 changes the movement direction of the service robot 1 (S210). For example, while maintaining the movement speed of the service robot 1, the autonomous movement control unit 73 changes the movement direction of the service robot 1 to the right direction or the left direction by about 5 degrees to 45 degrees in planar view. Since the robot arm 3 is backdrivable, the damage to be caused to the peripheral object is originally small. Accordingly, in the embodiment, the service robot 1 is not stopped, and only the slight change in the movement direction of the service robot 1 is merely performed. Thereby, the service robot 1 can arrive at the destination early.

[0055] Next, the route generation unit 72 updates the route (S220). That is, the route generation unit 72 once again generates the route from the current position of the service robot 1 to the destination, because the movement route of the service robot 1 has departed from the route generated in advance as described above.

[0056] Next, the autonomous movement control unit 73 determines whether the external force caused by the contact with the peripheral object has acted on the mobile carriage 5 during the movement of the service robot 1 using the mobile carriage 5 (S230). In the case where the autonomous movement control unit 73 determines that the external force has acted, the autonomous movement control unit 73 performs the emergency stop of the movement of the service robot 1 (S240). On the other hand, in the case where the autonomous movement control unit 73 determines that the external force has not acted, the autonomous movement control unit 73 causes the process to proceed to S250.

[0057] Next, the autonomous movement control unit 73 determines whether the service robot 1 has arrived at the destination (S250). In the case where the autonomous movement control unit 73 determines that the service robot 1 has arrived at the destination, the autonomous movement control unit 73 ends the process. In the case where the autonomous movement control unit 73 determines that the service robot 1 has not arrived at the destination, the autonomous movement control unit 73 returns the process to SI 60.

[0058] In the case where the autonomous movement control unit 73 has performed the emergency stop of the movement of the service robot 1 as described above (S240), the autonomous movement control unit 73 notifies an operator of the emergency stop of the service robot 1. The operator rushes to the service robot 1, and determines whether the movement of the service robot 1 can be continued. In the case where the operator determines that the movement of the service robot 1 can be continued, the operator restarts the movement of the service robot 1.

[0059] The embodiment of the present disclosure has been described above. The above embodiment has the following characteristics.

[0060] As shown in FIG. 1, FIG. 4, and FIG. 9, the service robot 1 (autonomous mobile object) includes the backdrivable robot arm 3, the robot body 4 that supports the robot arm 3, the mobile carriage 5 that is provided at the lower portion of the robot body 4, and the control unit 6 that controls the robot arm 3 and the mobile carriage 5. The control unit 6 executes the collision relaxation control when the external force caused by the contact with the peripheral object acts on the robot arm 3 during the movement of the service robot 1 using the mobile carriage 5. In the above configuration, the detection of the collision is performed by the backdrivable robot arm 3, which does not cause large damage to the peripheral object at the time of the contact with the peripheral object. Therefore, in the above configuration, the service robot 1 can move at a higher speed, compared to a case where the detection of the collision is performed by the bumper 21. Further, since large damage is not caused to the peripheral object, there is less restriction when the movement route of the service robot 1 is generated, and for example, it is not necessary to select an indirect route on which the number of walkers is very small.

[0061] Further, as shown in FIG. 9, the collision relaxation control is the control (S210) to change the movement direction of the service robot 1. With the configuration, it is possible to avoid the peripheral object without decreasing the movement speed of the service robot 1.

[0062] Further, for example, as shown in FIG. 5, the control unit 6 controls the robot arm 3 and the mobile carriage 5 such that the robot arm 3 is positioned forward of the robot body 4 in the movement direction of the service robot 1 during the movement of the service robot 1 using the mobile carriage 5. With this configuration, it is possible to efficiently detect the contact between the service robot 1 and the peripheral object.

[0063] Further, for example, as shown in FIG. 5, the control unit 6 controls the robot arm 3 such that the robot arm 3 protrudes forward of the mobile carriage 5 in the movement direction of the service robot 1 in planar view. With this configuration, it is possible to efficiently detect the contact between the service robot 1 and the peripheral object.

[0064] Further, for example, as shown in FIG. 5 to FIG. 7, the control unit 6 has a plurality of sensing modes including the first sensing mode 80 in which the attitude of the robot arm 3 is the first attitude shown in FIG. 5 and the second sensing mode 81 in which the attitude of the robot arm 3 is the second attitude in FIG. 6 that is different from the first attitude shown in FIG. 5. The control unit 6 selects one of the plurality of sensing modes. The control unit 6 controls the attitude of the robot arm 3 based on the selected sensing mode. With the above configuration, it is possible to realize different sensing ranges.

[0065] Further, as shown in FIG. 4 and FIG. 9, the service robot 1 further includes the camera 15 and Lidar 16 (peripheral environment monitoring unit) that monitor the peripheral environment. The control unit 6 selects one of the plurality of sensing modes based on the peripheral environment (S130, S140, S170, S180, S190). With the above configuration, it is possible to select an optimal sensing mode depending on the peripheral environment.

[0066] In the first attitude shown in FIG. 5, the height position of the end effector 35 of the robot arm 3 is the first height position Hl . In the second attitude shown in FIG. 6, the height position of the end effector 35 of the robot arm 3 is the second height position H2 different from the first height position Hl. With the above configuration, it is possible to perform sensing in ranges that are different in the vertical direction.

[0067] Further, for example, as shown in FIG. 8, the control unit 6 may swing the robot arm 3 in a fan-like manner during the movement of the service robot 1 using the mobile carriage 5. With this configuration, a wide-range sensing is realized.

[0068] Further, for example, as shown in FIG. 2, the robot arm 3 includes the upper arm link 30 and the forearm link 31 (at least two links), and the elbow joint 33 (joint) that couples the upper arm link 30 and the forearm link 31. The service robot 1 further includes the elbow joint actuator 41 (actuator) that is provided in the arm base 12 of the robot body 4 and that drives the elbow joint 33, and the endless belt 31b (dynamic power transmission mechanism) that transmits the dynamic power generated by the elbow joint actuator 41, to the elbow joint 33. With the above configuration, the weight reduction of the robot arm is realized. Accordingly, when the robot arm 3 of the service robot 1 comes into contact with the peripheral object, large damage is not caused to the peripheral object. Further, with the above configuration, the backdrivability of the robot arm 3 is realized at a high level.

[0069] Further, as the dynamic power transmission mechanism, for example, the endless belt 31b or the wire 35b can be employed. With this configuration, the weight reduction of the robot arm 3 is realized at a high level.

[0070] Further, the control unit 6 performs the impedance control of the robot arm 3. With this configuration, the backdrivable robot arm 3 can be realized by a simple control.

[0071] Further, as shown in FIG. 4 and FIG. 9, the service robot 1 further includes the bumper sensor 25 (contact sensor) that detects that the peripheral object has come into contact with the mobile carriage 5 during the movement of the service robot 1 using the mobile carriage 5. The control unit 6 may stop the movement of the service robot 1 when the bumper sensor 25 has detected that the peripheral object has come into contact with the mobile carriage 5 (S240). With the above configuration, it is possible to stop the movement of the service robot 1 when the mobile carriage 5 has come into contact with the peripheral object.

[0072] Further, as shown in FIG. 9, the control method for the service robot 1 includes starting the autonomous movement of the service robot 1 using the mobile carriage 5 (SI 50), and executing the collision relaxation control when the external force caused by the contact with the peripheral object acts on the robot arm 3 during the movement of the service robot 1 using the mobile carriage 5 (S210). With the above method, the high-speed movement of the service robot 1 is realized.

First Modification

[0073] Next, a first modification will be described with reference to FIG. 10. Points in which the modification is different from the above embodiment will be mainly described below, and repetitive descriptions will be omitted.

[0074] FIG. 10 shows a plan view of a service robot 1. As shown in FIG. 10, the robot arm 3 is positioned forward of the robot body 4 in the movement direction of the service robot 1. The forearm link 31 of the robot arm 3 is positioned forward of the mobile carriage 5 in the movement direction of the service robot 1 in planar view of FIG. 10. Moreover, the forearm link 31 extends in a direction orthogonal to the movement direction of the service robot 1 in planar view, and has a horizontally extending attitude. With the above configuration, it is possible to widen the sensing range in the width direction of the service robot 1. Further, as shown in FIG. 10, the link length of the forearm link 31 may be longer than the diameter of the mobile carriage 5. With this configuration, it is possible to realize a sensing range that is wide in the width direction of the service robot 1.

Second Modification

[0075] Next, a second modification will be described with reference to FIG. 11. Points in which the modification is different from the above embodiment will be mainly described below, and repetitive descriptions will be omitted.

[0076] As shown in FIG. 11, step SI 00 to step S200 coincide with those in the above embodiment, and therefore the descriptions are omitted.

[0077] The autonomous movement control unit 73 determines whether the external force caused by the contact with the peripheral object has acted on the robot arm 3 during the movement of the service robot 1 using the mobile carriage 5 (S200). In the case where the autonomous movement control unit 73 determines that the external force has acted, the autonomous movement control unit 73 causes the process to proceed to S300. In step S300, the autonomous movement control unit 73 decreases the movement speed of the service robot 1 (S300). When the service robot 1 is decelerated in this way, there is a possibility that the peripheral object goes away from the traveling direction of the service robot 1 while contacting with the service robot 1 and thereby the contact state is resolved. Accordingly, it is possible to maintain the movement speed of the service robot 1 in some degree, compared to the case of the emergency stop of the service robot 1. As a result, the service robot 1 can arrive at the destination early.

[0078] In the above second modification, in the case where the autonomous movement control unit 73 determines that the external force has acted (S200), the autonomous movement control unit 73 may temporarily decrease the movement speed of the service robot 1. To temporarily decrease the movement speed of the service robot 1 means that the movement speed is restored to the speed before the decrease when a predetermined time lapses after the movement speed of the service robot 1 is decreased or when a predetermined condition is satisfied after the movement speed of the service robot 1 is decreased.

[0079] In the above second modification, in the case where the autonomous movement control unit 73 determines that the external force has acted (S200), the autonomous movement control unit 73 may non-temporarily decrease the movement speed of the service robot 1. To non-temporarily decrease the movement speed of the service robot 1 means that the movement speed, in principle, is not restored to the speed before the decrease after the movement speed of the service robot 1 is decreased. It has been found that the environment in which the service robot 1 is currently moving is an environment in which there is a risk that the peripheral object comes into contact with the robot arm 3 during the movement of the service robot 1 using the mobile carriage 5. Therefore, after the above determination, an operation in which the movement speed of the service robot 1 is decreased by a predetermined degree regardless of whether the external force acts is possible.

[0080] The first modification and the second modification have been described above. The above embodiment can be further modified as described below.

[0081] For example, the control unit 6 may change a control parameter for the impedance control of the robot arm 3, depending on the movement speed of the service robot 1. Typically, the control parameter for the impedance control means inertia coefficient, viscosity efficient, or stiffness coefficient.

[0082] Further, as the dynamic power transmission mechanism that transmits the dynamic power generated by the elbow joint actuator 41 to the elbow joint 33, a link mechanism may be employed instead of the mechanisms illustrated in FIG. 2 and FIG. 3.

Third Modification

[0083] Next, a third modification will be described with reference to FIG. 12. Points in which the modification is different from the above embodiment will be mainly described below, and repetitive descriptions will be omitted.

[0084] In the above embodiment, as shown in FIG. 1, the control unit 6 is included in the service robot 1. That is, the control system 100 including the service robot 1 and the control unit 6 is realized by only the service robot 1.

[0085] In contrast, in the modification, a control system 300 includes a service robot 1 and a control device 200. The service robot 1 and the control device 200 are separately configured. The service robot 1 and the control device 200 are configured such that bidirectional communication can be performed. Moreover, the control device 200 executes some or all of the functions of the control unit 6 shown in FIG. 4. That is, the control unit 6 shown in FIG. 4 is realized through distributed processing by the service robot 1 and the control device 200. In this case, for example, the control unit 6 of the service robot 1 determines whether the external force caused by the contact with the peripheral object has acted on the robot arm 3 during the movement of the service robot 1 using the mobile carriage 5, and the control unit 6 of the service robot 1 sends the determination result to the control device 200. The control device 200 determines whether the execution of the collision relaxation control is necessary, based on the determination result received from the service robot 1. In the case where the control device 200 determines that the collision relaxation control is necessary, the control device 200 sends a collision relaxation control command to the service robot 1. The control unit 6 of the service robot 1 executes a predetermined collision relaxation control when receiving the collision relaxation control command from the control device 200.

[0086] In the above modification, whether the external force caused by the contact with the peripheral object has acted on the robot arm 3 during the movement of the service robot 1 using the mobile carriage 5 is determined by the control unit 6 of the service robot 1, but the present disclosure is not limited to this. Sensor signals of various sensors included in the service robot 1 may be sent to the control device 200 in real time. The control device 200 may determine whether the external force caused by the contact with the peripheral object has acted on the robot arm 3 during the movement of the service robot 1 using the mobile carriage 5, based on the received sensor signals.

Forth Modification

[0087] Next, a fourth modification will be described. Points in which the modification is different from the above embodiment will be mainly described below, and repetitive descriptions will be omitted.

[0088] In the above embodiment, as an example, the collision relaxation control is the control to decrease the movement speed of the service robot 1 or the control to change the movement direction of the service robot 1. However, the collision relaxation control is not limited to this.

[0089] For example, the collision relaxation control may be a control to stop the movement of the service robot 1.

[0090] Further, the control unit 6 may execute the collision relaxation control with a condition that the control unit 6 determines that the external force caused by the contact with the peripheral object has acted on the robot arm 3 during the movement of the service robot 1 using the mobile carriage 5, a predetermined number of times. With this configuration, it is possible to restrain the frequency of the execution of the collision relaxation control, and to give priority to the movement of the service robot 1. In this way, the timing of the execution of the collision relaxation control is not limited to the time point when it is determined that the external force caused by the contact with the peripheral object has acted on the robot arm 3 during the movement of the service robot 1 using the mobile carriage 5, and may be a time point after the time point of the determination. The reason why it is not necessary in this way to execute the collision relaxation control immediately at the time point when it is determined that the external force caused by the contact with the peripheral object has acted on the robot arm 3 during the movement of the service robot 1 using the mobile carriage 5 is because the robot arm 3 is configured to be backdrivable.

[0091] In the above-described examples, the program can be stored and supplied to a computer, using various types of non-transitory computer-readable media. The non-transitory computer-readable media include various types of tangible recording media. Examples of the non-transitory computer-readable media include a magnetic recording medium (for example, a flexible disc, a magnetic tape, and a hard disc drive) and a magneto-optical recording medium (for example, a magneto-optical disc). Examples of the non-transitory computer-readable media further include a CD-read only memory (ROM), a CD-R, a CD-R/W, and a semiconductor memory (for example, a mask ROM). Examples of the non-transitory computer-readable media further include a programmable ROM (PROM), an erasable PROM (EPROM), a flash ROM, and a random access memory (RAM). Further, the program may be supplied to the computer by various types of transitory computer-readable media. Examples of the transitory computer-readable media include an electric signal, an optical signal, and an electromagnetic wave. The transitory computer-readable media can supply the program to the computer through a wire communication path such as an electric wire and an optical fiber, or through a wireless communication path.

Claims

1. A control system comprising: an autonomous mobile object including a backdrivable robot arm, a robot body that supports the robot arm, and a mobile carriage that is provided at a lower portion of the robot body; and a control unit configured to execute a collision relaxation control in response to action of external force on the robot arm during movement of the autonomous mobile object using the mobile carriage, the external force being caused by contact with a peripheral object.

2. The control system according to claim 1, wherein the collision relaxation control is a control to change a movement direction of the autonomous mobile object.

3. The control system according to claim 1, wherein the collision relaxation control is a control to decrease a movement speed of the autonomous mobile object.

4. The control system according to claim 1, wherein the control unit is configured to control the robot arm or the mobile carriage such that the robot arm is positioned forward of the robot body in a movement direction of the autonomous mobile object during the movement of the autonomous mobile object using the mobile carriage.

5. The control system according to claim 4, wherein the control unit is configured to control the robot arm such that the robot arm protrudes forward of the mobile carriage in the movement direction of the autonomous mobile object in planar view.

6. The control system according to claim 1, wherein the control unit is configured to have a plurality of sensing modes including at least a first sensing mode and a second sensing mode, to select one of the plurality of sensing modes, and to control an attitude of the robot arm based on the selected sensing mode, the first sensing mode being a sensing mode in which the attitude of the robot arm is a first attitude, the second sensing mode being a sensing mode in which the attitude of the robot arm is a second attitude different from the first attitude.

7. The control system according to claim 6, wherein: the autonomous mobile object further includes a peripheral environment monitoring unit configured to monitor a peripheral environment; and the control unit is configured to select one of the plurality of sensing modes based on the peripheral environment.

8. The control system according to claim 6 or 7, wherein: in the first attitude, a height position of an end effector of the robot arm is a first height position; and in the second attitude, the height position of the end effector of the robot arm is a second height position different from the first height position.

9. The control system according to claim 1, wherein the control unit is configured to swing the robot arm in a fan-like manner during the movement of the autonomous mobile object using the mobile carriage.

10. The control system according to claim 1, wherein: the robot arm includes at least two links, and a joint that couples the at least two links; and the autonomous mobile object further includes an actuator configured to drive the joint, the actuator being provided in the robot body, and a dynamic power transmission mechanism configured to transmit dynamic power generated by the actuator, to the joint.

11. The control system according to claim 10, wherein the dynamic power transmission mechanism includes a belt or a wire.

12. The control system according to claim 1, wherein the control unit is configured to perform an impedance control of the robot arm.

13. The control system according to claim 1, further comprising a contact sensor configured to detect that the peripheral object has come into contact with the mobile carriage during the movement of the autonomous mobile object using the mobile carriage, wherein the control unit is configured to stop movement of the autonomous mobile object when the contact sensor has detected that the peripheral object has come into contact with the mobile carriage.

14. A control method for an autonomous mobile object, the autonomous mobile object including a backdrivable robot arm, a robot body that supports the robot arm, and a mobile carriage that is provided at a lower portion of the robot body, the control method comprising: moving the autonomous mobile object using the mobile carriage; and executing a collision relaxation control in response to action of external force on the robot arm during movement of the autonomous mobile object using the mobile carriage, the external force being caused by contact with a peripheral object.

15. A storage medium storing instructions that are executable by one or more processors of a computer and that cause the one or more processors to perform functions comprising the control method according to claim 14.