GB2629369A

GB2629369A - Robot

Info

Publication number: GB2629369A
Application number: GB2306064.3A
Authority: GB
Inventors: Alexander Eccleston James; Zenti Marco; Abraham George Agish; Eric Hutton Jack; Thivet Rémi
Original assignee: Dyson Technology Ltd
Current assignee: Dyson Technology Ltd
Priority date: 2023-04-25
Filing date: 2023-04-25
Publication date: 2024-10-30
Also published as: CN120982013A; GB202306064D0; WO2024224196A1

Abstract

A robot 100, typically a walking robot, has a body 110, at least four legs 121, 122, 123, 124 for locomotion of the robot, a plurality of multiphase motors 140, 150 to operate the legs, and electronic circuitry to control the plurality of motors. The electronic circuitry is configured to short-circuit at least two phases of a motor in the absence of electrical power being supplied to this motor. Preferably, three motors are provided for each leg, for example with each leg having a joint. A locomotion controller may be provided so that the robot is in a collapsed configuration if a fault is detected relating to this motor, and tipping detection may be provided so that power is provided to other motors so as to oppose tipping motion.

Description

ROBOT

BACKGROUND

Robots capable of operating in a domestic or commercial environment, e.g. a home or a hotel, are known. Applications of such robots include vacuum cleaning and floor mopping.

Some known examples of such robots are wheeled, with a body carried close to the ground by wheels in an underside of the body.

SUMMARY

Legged robots, such quadrupeds or hexapods, are known. A legged robot has a body supported on legs, providing greater ground clearance and improved traversal capabilities than may be achievable for wheeled robots. For example, in a domestic environment there may be many obstacles, such as a step or stairs, preventing access to a wheeled robot whereas a legged robot may be able to traverse such obstacles.

However, legged robots may be inherently more unstable than a wheeled robot. For example, a legged robot may fall over on a wet floor, trip over an obstacle, or be pushed over. Also, a technical fault affecting locomotion of a legged robot, such as a loss of power, may cause the robot to fall over. Furthermore, the size and weight of a legged robot that may be required to climb stairs, e.g. steps of 220 millimetres height, may require a comparatively heavy power system and motors for desired manoeuvrability and sufficient runtime. Serious injury may be caused by such a robot falling on, e.g., a person's foot or leg.

Moreover, unlike settings typical for industrial robots, people and pets in a domestic environment may not have training or awareness of risks associated with robots operating in the same environment. Unlike actors that the robot might encounter in an industrial / commercial setting, actors in a domestic environment are not expected to be bound by any rules (e.g. "do not enter if the robot is operating") or if there are rules, it is not expected that all actors would obey those rule at all times (e.g. an infant or a complacent adult) and their behaviour may be unpredictable (especially to a robot). Furthermore, vulnerable people may not be able to move out of the way when danger s imminent (e.g. an infant or an elderly person).

Operating legged robots in a domestic environment, and also in a commercial environment, may therefore require improved safety measures relating to the operation of such robots to reduce the risk of injury or damage caused by the robots.

According to a first aspect, there is provided a robot comprising a body; at least four legs for locomotion of the robot; a plurality of multiphase motors to operate the legs; electronic circuitry to control the plurality of motors; wherein the electronic circuitry is configured to, in the absence of electrical power being supplied to a motor of the plurality of motors, short-circuit at least two phases of said motor.

In the absence of supply of electrical power, for example as a result of an unexpected loss of power or a controlled cut of power to a motor, said motor may spin largely unimpeded. As such, a leg controlled by said motor could collapse under the weight of the robot, possibly resulting in a forceful impact of the robot. By shorting at least two phases of the motor, said motor becomes configured to resist motion, resulting from the counter-electro-motive force from the spinning motor. Thus, said motor may arrest the fall of the robot and hence reduce the force of the impact.

The robot may comprise a power controller configured to control supply of electrical power to said motor.

The power controller may be configured to stop the supply of electrical power to said motor in response to detection of a fault condition related to said motor.

During operation of the robot, a fault condition may arise which indicates that a fault may have occurred. In response to a fault condition related to operation of a particular motor, it is possible to effect a controlled cut of electrical power to said motor. For example, where the fault condition indicates that operation of said motor is unsafe, the cut of power may be triggered, thereby causing the short-circuiting of the at least two phases of said motor.

The power controller may be a logical unit and may be implemented with other logical units as single hardware controller, e.g. a microcontroller.

The electronic circuitry within the motor assembly may be configured to detect an anomaly resulting from a fault within itself and automatically trigger the short-circuiting of the at least two phases of said motor even if the power controller has not cut power to the faulty motor.

The power controller may be configured to stop the supply of electrical power to said motor in response to detection of a fault condition associated with communication signals relating to said motor.

Communication signals relating to a motor may indicate a fault condition. For example, the contents of a communication signal may detail the fault condition, or the absence of a communication signal may indicate the fault condition. In such a situation, the power controller is configured to stop supply of electrical power since operation of the motor may be deemed unreliable and unsafe under such circumstances.

The electronic circuitry may be configured to, for each motor of the multiple motors, in the absence of electrical power being supplied to the motor, short-circuit at least two phases of the motor.

The power controller may be configured to stop supply of electrical power to the plurality of motors in response to detection of a fault condition related to the plurality of motors.

Where a fault condition indicates that operation of the plurality of motors is unsafe, a cut of power may be triggered for all motors. Such a fault condition may be, for example, related to the condition of a battery supplying electrical power to the motors, or a problem with an individual motor. Following cutting of power to the plurality of motors, the legs will collapse with the motors resisting this motion and hence slowing descent of the robot.

The power controller may be configured to control the supply of electrical power to a set of motors of the plurality of motors, i.e. more than one motor but not necessarily all motors. In such a case, the power controller may be configured to control the supply of electrical power to each motor of the set of motors.

The robot may comprise a locomotion controller configured to control the plurality of motors.

The locomotion controller may be a logical unit and may be implemented with other logical units as single hardware controller, e.g. a microcontroller.

The locomotion controller may be configured to control one or more other motors of the plurality of motors to cause the robot to assume a collapsed configuration in response to detection of a fault condition relating to said motor.

Motors which are considered operational, in that the fault condition is not deemed to affect these motors, can be controlled to cause the robot to assume a collapsed configuration. By controlling the operational motors to do so, the severity of the impact of the robot may be reduced.

The locomotion controller may be configured to control the one or more other motors by supplying power to the one or more other motors to cause the robot to assume a collapsed configuration in response to detection of a fault condition relating to said motor.

It may be possible to actively control the motors that are deemed operational, in that power can be supplied to the one or more other (operational) motors, to achieve the collapsed configuration (i.e without necessarily cutting power to those motors).

Said motor may be configured to operate a first joint of a first leg of the robot. The locomotion controller may be configured to control another motor configured to operate a second joint of the first leg in response to detection of the fault condition. Additionally or alternatively, the locomotion controller may be configured to control another motor configured to operate a joint of a second leg in response to detection of the fault condition Upon detection of a fault condition, another motor (or motors) relating to the same leg and/or another motor (or motors) relating to another leg (or legs) can be controlled by the locomotion controller.

The locomotion controller may be configured to detect or determine a tipping motion of the robot as a result of the absence of power being supplied to said motor.

The locomotion controller may control the one or more other motors, by supplying power to the one or more other motors, to move the body so as to oppose the tipping motion of the robot.

The shorting of the phases of said motor may reduce severity of impact but may in some scenarios not prevent the robot from tipping. By actively controlling (i.e. by supplying power to) the other motors to move the robot body in order to oppose the tipping motion, it may be possible to oppose the tipping motion and it may even be possible to prevent tipping altogether whilst bringing the robot into the collapsed configuration.

The locomotion controller may be configured to adjust a damping value of at least one motor from a first value to a second value in order to adjust an amount by which the at least one motor is configured to resist motion.

The damping value applied to any motor that is operational (i.e. other than said motor or motors which have shortened phases) can be controlled and suitably adjusted while the robot is collapsing. Such adjustment of the damping value may further decrease severity of impact.

The locomotion controller may be configured to actively control one or more of the other motors to encourage the robot to collapse within its own footprint.

The robot may comprise a communication controller. The communication controller may be a logical unit and may be implemented with other logical units as single hardware controller, e.g. a microcontroller.

The communication controller may be configured to receive communication signals relating to each of the motors. Detection of a safety relevant fault in a communication signal relating to a motor may be a fault condition relating to said motor. Such safety relevant faults may include corrupt data packets, out of sequence packets, lost data packets, implausible/out of range values (e.g. for joint position, velocity, torque, or motor temperature), or having excessive latency, or the absence of a communication signal.

The communication controller may be configured to regularly receive communication signals relating to at least one of the motors. The communication controller may be configured to receive communication signals relating to some or all of the plurality of 15 motors.

The absence of a communication signal relating to a motor may be a fault condition relating to said motor.

The electronic circuitry may be configured to short-circuit the at least two phases of said motor after a time tl in the absence of power.

The communication controller may be configured to determine a fault condition that communication signals relating to said motor have terminated after a time t2.

The time t2 may be shorter than the time tl.

The electronic circuitry that responds to the absence of power by short-circuiting the phases may do so slower than the communications controller can detect the termination of communication signals relating to said motor. Thus, contingency measures may already be put into effect, e.g. by the locomotion controller, to handle the expected collapsing of the robot.

Short-circuiting the at least two phases may cause said motor to resist motion with a damping factor in a range of 0.1 to 20 N*m*s/rad (Newtons*metres*seconds/radians).

The damping factor in the specified range may be small enough to reduce the likelihood of overdamping, which may cause the robot tipping over, and yet large enough to significantly reduce impact forces.

The motors of the plurality of motors may be three-phase motors.

The plurality of motors may include three motors to operate each leg.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a robot; Figure 2 is a perspective view of a leg of the robot of Figure I; Figure 3 is an illustration of an actuator module including electronic circuitry of the robot of Figure 1; Figure 4 is another illustration of the actuator module including the electronic circuitry of Figure 3 in an alternative configuration; Figure 5 is an illustration of a controller system of the robot of Figure 1; Figure 6 is a perspective view of the robot of Figure 1 in a collapsed configuration; Figure 7 is a perspective view of the robot of Figure 1 in an overturned configuration; Figure 8 is another perspective view of the robot of Figure 1 in another overturned configuration; Figure 9 is an illustration of electronics hardware of the robot of Figure 1; Figure 10 is another illustration of the hardware of Figure 9 experiencing a fault condition; Figure 11 is another illustration of the hardware of Figure 9 experiencing a fault condition; Figure 12 is another illustration of the hardware of Figure 9 experiencing a fault condition.

DETAILED DESCRIPTION

Figure 1 shows a perspective view of a robot 100. In some examples, the robot 100 may be configured for operating in a domestic environment or in a commercial environment; indoors or outdoors. As such, safety of operation of the robot 100 and, correspondingly, reduction of risk of injury to people or damage to objects caused by a fault in the robot 100 may be desirable. Legged robots, such as the robot 100, may be more unstable than wheeled robots and more likely to collapse and even overturn. As is detailed below, the robot 100 is configured to slow the collapsing of the robot 100 and decrease the likelihood of overturning.

Thus, the force of an impact may be reduced and an area potentially affected by the impact may be reduced in size. This may reduce severity of an injury to a person, and the likelihood for a person to be injured.

The robot 100 has a body H 0 (or torso'). The body 1 1 0 is for accommodating hardware components of the robot 100, such as a battery supplying electrical power or electronics for controlling the robot 100.

The body 110 has a front end 1 1 1 (or 'first end') and, opposite thereto, a rear end 112 (or 'second end'). The body 110 has a left side 113 (or 'first side') and, opposite thereto, a right side 114. The body 110 has a topside 115 and, opposite thereto, an underside 116. In use, for example during traversal, the underside 116 faces toward a support surface 1000, e.g. a floor, on which the robot 100 is supported.

The robot 100 has a plurality of at least four legs 120 for locomotion of the robot 100. By means of the plurality of legs 120, the robot 100 is capable of moving around, for example in order to perform an operation in different locations or whilst moving around. As depicted in Figure 1, the robot 100 has four legs. The exemplary robot 100 is thus a quadruped, i.e. a legged robot with four legs. The present disclosure is not limited to quadrupeds, however, but equally applicable to robots with any number of at least four legs, such as a hexapod with six legs.

The plurality of legs 120 includes a first leg 121, a second leg 122, a third leg 123, and a fourth leg 124. As shown in Figure 1, the first leg 121 is a front left leg, the second leg is a front right leg, the third leg 123 is a rear left leg, and the fourth leg 124 is a rear right leg.

The front legs 121, 122 are provided towards the front end 111 of the body 110, while the rear legs 123, 124 are provided towards the rear end 112 of the body 110. Similarly, the left legs 121, 123 are provided towards the left side 113, while the right legs 122, 124 are provided towards the right side 114.

The robot 100 includes a plurality of actuator modules 140 to operate the plurality of legs 120.

The robot 100 includes plurality of motors 150 provided in the plurality of actuator modules 140. The motors 150 are electrical motors with multiple phases, for example three phases, arranged to control various degrees of freedom in the legs 120.

The robot 100 includes electronic circuitry 160 for each of the motors 150 to control the plurality of motors 150. The electronic circuitry 160 controls the motors 150 to cause operation of the legs 120 such that locomotion of the robot 100 may be achieved.

Figure 2 illustrates the configuration of the first leg 121 of the plurality of legs 120, including also the motors to operate the first leg 121. Although Figure 2 shows only a single leg, the other legs are configured correspondingly and the same description and illustrations are applicable also to the other legs.

Each leg 121, 122, 123, 124 of the plurality of legs 120 includes an upper leg 125 and a lower leg 126, and terminates in a foot 127. In use, the feet 127 engage the support surface 1000.

Each leg of the plurality of legs 120 is articulated. Each upper leg 125 is articulated about the body 110, and the upper leg 125 and the lower leg 126 are articulated. Articulation of the plurality of legs 120 is controlled by means of the plurality of actuator modules 140. The plurality of actuator modules 140 includes, for each leg, a first actuator module 142, a second actuator module 144, and a third actuator module 146.

The plurality of motors 150 includes, for each leg, a first motor 152, a second motor 154 and a third motor 156. Suitably each motor of the plurality of motors 150 is configured to cause rotation of a rotor 1501 relative to a stator 1502.

The first motor 152 is part of the first actuator module 142. The second motor 154 is part of the second actuator module 144. The third motor 156 is part of the third actuator module 146.

The first actuator module 142 is configured to control hip roll. The second actuator module 144 is configured to control hip pitch. The third actuator module 146 is configured to control knee pitch.

In total, the robot 100 has three motors 152, 154, 156 per leg 121, 122, 123, 124 giving a plurality of twelve motors 150, but a different total number of motors may be provided, e.g. 18 for a hexapod.

In the absence of electrical power to an electrical motor for example as a result of an unexpected loss of power or a controlled cut of power, said electrical motor may spin largely unimpeded. As such, a robot with a leg controlled by said electrical motor could collapse under the weight of the robot. The robot 100, however, includes the electronic circuitry 160 which is configured to slow the collapsing of the robot 100 in such circumstances. More particularly, the electronic circuitry 160 is configured to short-circuit the phases of a motor if said motor is not being supplied with electrical power. By shorting the phases of said motor, the motor becomes configured to resist motion, i.e. rotation of the rotor 1501 relative to the stator 1502. Hence, said motor may slow the collapsing of the robot 100. In some examples, the electronic circuitry 160 is configured to short-circuit some, but not all, of the phases of the motor. In some examples, the electronic circuitry 160 is configured to short-circuit all of the phases, which may result in a greater damping effect than short-circuiting some, but not all, of the phases. Further, the resistance to motion due to short-circuiting of the phases may increase with increasing rotational velocity of the motor and decrease with decreasing rotational velocity, thereby providing a breaking effect dependent on the rate at which the robot is collapsing.

Short-circuiting the phases of said motor is understood to mean an electrical connection being made between the phases with comparatively low electrical resistance such that a counter-electromotive force (also referred to as back EMT) is generated to oppose the rotation of the motor. Such short-circuiting may be implemented by making an electrical connection between lines carrying the phases or terminals of the motor receiving the phases.

The short-circuiting of the phases of a motor causes said motor to experience damping, where the amount of damping experience (e.g. the damping factor) may be in a range of 0.1 to 20 Nm*s/rad (Newton-metres divided by radians per second). The damping factor in the specified range may be small enough so as to avoid overdamping, which may cause tipping of the robot, and yet large enough to significantly arrest the fall of the robot.

Figures 3 and 4 show the first actuator module 142, including the electronic circuitry 160 for controlling the first motor 152 and, in particular, short-circuiting the phases of the first motor 152. For purposes of illustration, only first actuator module 142 is shown, and hence only the relevant circuitry for controlling the first motor 152 is shown in Figures 3 and 4 but the second actuator module 144 and the third actuator module 146 are configured likewise.

In Figure 3, a first configuration of the electronic circuitry 160 is depicted whereby the electronic circuitry 160 supplies electrical power to the first actuator module 142. By contrast, in Figure 4 a second configuration of the electronic circuitry 160 is shown where the phases of the motor 152 are short-circuited.

The electronic circuitry 160 is configured to short-circuit the phases of the motor 152 in the absence of electrical power being supplied to the motor 152. Absence of electrical power to a motor or multiple motors may occur in operation due to a fault, for example a failure of the battery directly resulting in no power, or a deliberate cutting of power in response to a fault condition indicating that a fault may have occurred.

The electronic circuitry 160 is configured to automatically short-circuit the phases of a motor in the absence of power being supplied to said motor. That is to say, the absence of power causes the electronic circuitry 160 to short-circuit the phases of said motor. Thus the electronic circuitry 160 does not require a control signal to short-circuit the phases. There may be a time delay between power supply ceasing and the electronic circuitry 160 causing the short-circuiting.

The electronic circuitry 160 is configured to passively short-circuit the phases of said motor.

That is to say, electrical power is not needed for the electronic circuitry 160 to short-circuit the phases. Thus the electronic circuitry 160 does not require an independent power source for the switching elements 168.

The electronic circuit 160 includes a microcontroller 161 ("MCU") for generating a pulse width modulation signal 162 to both commutate the multi-phase motor and to modulate the power produced by the electric motor.

The electronic circuitry 160 includes a gate driver 163 for generating a high-current drive signal 164 for control of switching elements.

The electronic circuitry 160 includes a power stage 165 for switching the polarity of the voltage +Vmot supplied to the first motor 152 via 3-phase terminals 167.

In some examples, the microcontroller 161, the gate driver 163 and the power stage 165 are provided together as a motor controller 166.

The electronic circuitry 160 includes a plurality of switching elements 168. The switching elements 168 are configured to short-circuit the three phases of the first motor 152 in the absence of electrical power being supplied to the motor 152. Suitably, electrical power is not required for operation of the switching elements 168, i.e. the switching elements 168 are "passive".

The switching elements 168 may be provided as an electro-mechanical relay or a solid-state relay (with normally closed contacts) or any suitable electronic circuity to short-circuit at least two phases of the first motor 152 in the absence of electrical power being supplied.

Equivalent circuitry is provided for the second motor 154 and the third motor 156, and all legs 120 are configured correspondingly.

In Figure 4, the short-circuited configuration of the electronic circuitry 160 is illustrated. The switching elements 168 are configured to change from the short-circuited configuration to their open position shown Figure 3 when the voltage supplied to the terminals 166, i.e. +Vmot, exceeds a predetermined threshold voltage greater than zero.

Figures 3 and 4 also show a gearbox 149 wherein the gearbox 149 and the motor 152 are connected by an input shaft.

Figure 5 illustrates a controller system 170 for controlling the robot 100. The controller system 170 is represented a logical system comprising multiple logic units 172, 174, 176. A corresponding hardware implementation may involve one or multiple physical units. An exemplary hardware implementation is illustrated in Figures 9 to 12.

The controller system 170 comprises a power controller 172. The power controller 172 is configured to control supply of electrical power to the plurality of motors 150. More particularly, the power controller 172 determines, for each motor, whether electrical power can be supplied. The power controller 172 may stop (or disable) the supply of electrical power to a motor in response to detection of a fault condition related to said motor. Stopping the supply of electrical power to a given motor triggers the switching elements 168 to short-circuit the phases of this motor.

The controller system 170 comprises a communication controller 174 configured to receive communication signals relating to the motors 150. The communication signals may be transmitted via wired or wireless means of communication. The communication signals may be transmitted, for example, directly by the plurality of motors 150 or by the actuator modules 140. Suitably, the actuator modules 140 may include communication modules. The actuator modules 140 may further include diagnostic hardware configured to monitor operation of the motors 150.

Communication signals may indicate fault conditions, for example, by containing corrupt data packets, out of sequence packets, lost data packets, implausible/out of range values (e.g. for joint position, velocity, torque, or motor temperature), or having excessive latency. Another example of a fault condition, which is described in detail below, relates to the absence of communication signals.

The communication controller 174 is configured to regularly receive communication signals relating to each of the motors 150. The absence of a communication signal is a fault condition relating to said motor. Upon the fault condition occurring, the power controller 172 may stop supply of electrical power to said motor.

When power is not anymore being supplied to said motor, the electronic circuitry 160 short-circuits the phases of said motor after expiry of an interval of time tl. That is to say, the electronic circuitry 160 has a response time corresponding to the time tl.

The communication controller 174 is configured to receive communication signals at regular intervals of time t2. The communication controller 174 determines the absence of a communication signal after time t2 has passed, by which time no further communication signal was received.

The time tl, i.e. the response time of the electronic circuitry 160 to a loss of power, is longer than the time t2 after which the communication controller 174 determine a fault condition.

This means that communication controller 174 may trigger contingency measures before the electronic circuitry 160 responds to the absence of power.

The controller system 170 comprises a locomotion controller 176 configured to control the plurality of actuator modules 140 including the motors 150 to achieve locomotion, i.e. coordinated operation of the plurality of legs 120 by means of the plurality of motors 150. Suitably, the locomotion controller 176 generates control signals to achieve a desired motion of the plurality of legs 120, such as the torque necessary for lifting the foot 127 of the front left leg 121.

When a fault condition arises, the locomotion controller 176 may actively control any motors unrelated to the fault condition, i.e. those motors deemed fully operational. For example, in a situation where communication with the first motor 152 of the left front leg 121 is lost, and giving rise to a corresponding fault condition, the locomotion controller 176 may actively control the other motors 154, 156 of the left front leg 121 and the motors of all other legs 122, 123, 124 in response to the fault condition. In particular, the locomotion controller 176 may control the motors deemed fully operational to reduce severity of the expected impact due to loss of power to the first motor 152. The locomotion controller 176 may further encourage the robot 100 to collapse vertically downward as opposed to tipping, thereby reducing the area affected by the expected impact. Tipping of the robot 100 may involve a forward or backward or sideways motion that will cause the robot 100 to fall on its side or even roll.

The locomotion controller 176 is configured to detect or determine a tipping motion using a suitable sensor or estimation means. For example, the locomotion controller 176 may detect the tipping motion using an accelerometer, or may determine the tipping motion based on information contained in the communication signals received by the communication controller 174.

Passive and active control of the motors 150 may be used in combination or as alternatives. In a situation where one motor experiences an absence of power, said motor will be passively controlled by the short-circuiting of the motor phases, but the remaining motors 150 may be controlled passively (by cutting power and triggering the switching elements 168) or actively (by the locomotion controller 176).

Figure 6 shows the robot 100 in a collapsed configuration, while in Figure 1 the robot 100 is shown in a standing configuration. In the standing configuration, the plurality of legs 120 is extended, providing ground clearance between the ground 1000 and the underside 116 of the body 110. In the collapsed configuration shown in Figure 6, the body 110 rests the plurality of legs 120 with each leg collapsed and ground clearance substantially reduced. As such, the robot 100 is said to have collapsed within its own footprint.

Where the robot 100 collapses within its own footprint, the collapsing of the robot 100 affects a comparatively small area, indicated in Figure 6 by a small impact area 1100. By contrast, were the robot 100 to tip as a result of a fault, a comparatively larger area would be affected, indicated in Figure 6 by a large impact area 1200. As a result of a tipping motion, for example residual forward motion at the time of a fault arising with respect to one of the motors 150, the robot 100 could tip over and come to rest anywhere within the large impact area 1200.

The locomotion controller 176 may actively control the motors remaining operational, by supplying power to the remaining motors, to move the body 110 so as to oppose a tipping motion of the robot 100. This may involve, for example, actively retracting one or multiple legs 120 in order to oppose the tipping motion. As a result, the large impact area 1200 may be reduced to the small impact area 1100, thereby reducing the area whereby the risk of injury to a person is increased. Also, the magnitude of the forces exerted by the robot 100 when collapsing may be reduced by causing the robot 100 to move slower.

The locomotion controller 176 may control the motors remaining operational by adjusting a damping value of the motors from a first value to a second value, thereby adjusting the amount by which the motors are configured to resist motion. For example, the locomotion controller 176 may reduce the damping value of a motor to promote collapsing of the respective leg in order to oppose a tipping motion experienced by the robot 100.

Figures 7 and 8 show the robot 100 in fallen configurations. In Figure 7, the robot 100 has tipped over and rests on the topside 115 of the robot 100. In Figure 8, the robot 100 has tipped over and rests on the left side 113. In general, the robot 100 could fall and come to rest on either side 113, 114 or the topside 115 of the robot 100. By means of the contingency measures described above the likelihood of the robot 100 tipping, or tipping and rolling, may be reduced.

Figure 9 schematically illustrates an exemplary hardware configuration of electronics to control the robot 100.

The power controller 172 and the communications controller 174 are provided together in a power and communications distribution system (abbreviated "PCD" system).

The communications controller 174 of the PCD system is in bi-directional communication with the motors 150 of the legs 120. As shown in Figure 9, the communications controller 174 is in bi-directional communication with the first actuator module 142 including the first motor 152, the second actuator module 144 including the second motor 154, and the third actuator module 146 including the third motor 156. The communications controller 174 is likewise in bi-directional communication with the actuator modules 140 of the second leg 122, the third leg 123, and the fourth leg 124.

The communications controller 174 is further in bi-directional communication with the locomotion controller 176.

A battery management system 190 supplies power to the PCD system from which power is distributed to the legs 120 and, in particular, the actuator modules 140 including the motors 150.

The locomotion controller 176 is in bi-directional communication with the communications controller 174 of the PCD system.

Figures 10, 11 and 12 illustrate exemplary faults in the schematic hardware configuration of Figure 9.

In Figure 10, supply of power to the PCD system is interrupted (represented by the broken arrow from the battery management system 190 to the PCD system), resulting in a loss of power to all motors 150. In such a situation, the locomotion controller 176 is unable to control any of the motors 150. The electronic circuitry 160 will instead passively short-circuit the phases of all motors 150.

In Figure 11, power to the third actuator module 146 of the first leg 121 is interrupted (represented by the broken arrow from the PCD system to the third actuator module 146). In such a situation, the locomotion controller 176 is able to actively control all other motors 150. Alternatively, the power controller 172 may stop supply of power to any of the other motors 150. As a result, active control would not be possible anymore and the electronic circuitry 160 will instead short-circuit the relevant phases.

In Figure 12, communication with the second actuator module 144 and the third actuator module 146 of the first leg 121 is interrupted (represented by the broken double-headed arrow connecting the communications controller 174 and the second and third actuator modules). As a result, the respective electronic circuitry 160 short-circuits the phases of the second motor 154 and the third motor 156 of the first leg 121. Also, the communications controller 174 will not receive further communication signals from the second actuator module 144 or the third actuator module 146 of the first leg 121. The absence of communication signals is deemed a fault condition, as a result of which the power controller 172 and the locomotion controller 176 may implement contingency measures, such as deliberately cutting power to or actively controlling of one or more remaining motors 150.

In the examples described with reference to the Figures, the actuator modules 140 are shown at specific locations, but this is for illustration only. In some examples, the actuator modules 140 may be provided at other locations and, e.g., utilise a belt drive to operate the corresponding joint. For example, the third actuator module 146, which is configured to control knee pitch, may be in the same location as the second actuator module 144.

In some examples, at least some components of the actuator modules 140 may be spaced apart from other components of the actuator modules 140. For example, components such as the motor drivers may be located, e.g., in the robot body 110 whereas the motors 150 may be located at or towards the joints.

Claims

CLAIMS1. A robot, comprising: a body; at least four legs for locomotion of the robot; a plurality of multiphase motors to operate the legs; electronic circuitry to control the plurality of motors; wherein the electronic circuitry is configured to, in the absence of electrical power being supplied to a motor of the plurality of motors, short-circuit at least two phases of said motor.
2. The robot according to claim 1, further comprising a power controller configured to control supply of electrical power to said motor; wherein the power controller is configured to stop the supply of electrical power to said motor in response to detection of a fault condition related to said motor.
3. The robot according to claim 2, wherein the power controller is configured to stop the supply of electrical power to said motor in response to detection of a fault condition associated with communication signals relating to said motor.
4. The robot according to claim 2 or 3, wherein the power controller is configured to control the supply of electrical power to the plurality of motors; wherein the electronic circuitry is configured to, for each motor, in the absence of electrical power being supplied to the motor, short-circuit at least two phases of the motor; and wherein the power controller is configured to stop supply of electrical power to the plurality of motors in response to detection of a fault condition related to the plurality of motors.
5. The robot according to any preceding claim, further comprising: a locomotion controller configured to control the plurality of motors; wherein the locomotion controller is configured to control one or more other motors of the plurality of motors to cause the robot to assume a collapsed configuration in response to detection of a fault condition relating to said motor.
6. The robot according to claim 5, wherein the locomotion controller is configured to control the one or more other motors by supplying power to the one or more other motors to cause the robot to assume a collapsed configuration in response to detection of a fault condition relating to said motor.
7. The robot according to claim 5 or 6, wherein wherein said motor is configured to operate a first joint of a first leg; wherein the locomotion controller is configured to control another motor configured to operate a second joint of the first leg in response to detection of the fault condition, and/or control another motor configured to operate a joint of a second leg in response to detection of the fault condition.
8. The robot according to any one of claims 5 to 7, wherein the locomotion controller is configured to: detect or determine a tipping motion of the robot as a result of the absence of power being supplied to said motor; and control the one or more other motors, by supplying power to the one or more other motors, to move the body so as to oppose the tipping motion of the robot.
9. The robot according to any one of claims 5 to 8, wherein the locomotion controller is configured to adjust a damping value of at least one motor from a first value to a second value in order to adjust an amount by which the at least one motor is configured to resist motion.
10. The robot according to any one of claims 5 to 9, wherein the locomotion controller is configured to actively control one or more of the other motors to encourage the robot to collapse within its own footprint.
11. The robot according to any preceding claim, further comprising: a communication controller configured to receive communication signals relating to each of the motors, and wherein detection of a safety relevant fault in a communication signal relating to a motor is a fault condition relating to said motor.
12. The robot according to claim 11, wherein the electronic circuitry is configured to short circuit the at least two phases of said motor after a time tl in the absence of power; wherein the communication controller is configured to determine a fault condition that communication signals relating to said motor have terminated after a time t2; and wherein the time t2 is shorter than the time tl.
13. The robot according to any preceding claim, wherein short-circuiting the at least two phases causes said motor to resist motion with a damping factor in a range of 0.1 to 20 20 N*m*s/rad.
14. The robot according to any preceding claim, wherein the plurality of multiphase motors is a plurality of three-phase motors.
15. The robot according to any preceding claim, wherein the plurality of motors includes three motors for each leg.