Integrated high-speed torque control system for a robotic joint
A control system for achieving high-speed torque for a joint of a robot includes a printed circuit board assembly (PCBA) having a collocated joint processor and high-speed communication bus. The PCBA may also include a power inverter module (PIM) and local sensor conditioning electronics (SCE) for processing sensor data from one or more motor position sensors. Torque control of a motor of the joint is provided via the PCBA as a high-speed torque loop. Each joint processor may be embedded within or collocated with the robotic joint being controlled. Collocation of the joint processor, PIM, and high-speed bus may increase noise immunity of the control system, and the localized processing of sensor data from the joint motor at the joint level may minimize bus cabling to and from each control node. The joint processor may include a field programmable gate array (FPGA).
1. A control system for use with a robot having a plurality of joints each driven by at least one motor, the control system comprising:
a top-level controller configured to generate task-based control input signals to thereby command execution of a required task;
a brainstem configured to process the task-based control signals to thereby determine which of the joints to activate to execute the required task, and to coordinate the motion of the activated joints; and
a joint-level controller in communication with the brainstem and having a plurality of printed circuit board assemblies (PCBAs), wherein each PCBA includes a joint processor and a high-speed bus providing a calibrated data transfer rate between itself and the brainstem;
wherein each PCBA is configured to control a torque output of the at least one motor only of a corresponding one of the joints using a high-speed feedback torque control loop of at least approximately 10 KHz, and wherein the brainstem provides both Cartesian space control and impedance-based control of the robot without also controlling the torque output.
2. The control system of claim 1 , wherein the joint-level controller includes a plurality of position sensors configured to determine a position and torque of the joints as respective analog signals, and wherein each PCBA includes a converter chip configured to convert the analog signals to corresponding digital signals, and to communicate the digital signals to the joint processor.
3. The control system of claim 1 , wherein each PCBA is embedded within the robot and collocated with the joint being controlled by that particular PCBA.
4. The control system of claim 1 , wherein the joint processor includes a field-programmable gate array (FPGA).
5. The control system of claim 4 , wherein the FPGA includes a plurality of processing chips, and wherein the PCBA has a steady-state power density of approximately 130 W/in 2 to approximately 400 W/in 2 .
6. A printed circuit board assembly (PCBA) for controlling the torque output of a motor-driven joint in a robot, the robot having a control circuit adapted for providing both Cartesian control and impedance-based control of the robot without also controlling the torque output, the PCBA comprising:
a joint processor; and
a high-speed bus providing a calibrated data transfer rate between the PCBA and a brainstem;
wherein the motor-driven joint is driven by at least one joint motor, and wherein the PCBA is configured to provide feedback-based torque control of the at least one joint motor in a control loop of at least approximately 10 KHz, and to receive data output from the brainstem at a rate of less than approximately 400 Hz, wherein the data output describes the Cartesian control and the impedance-based control.
7. The PCBA of claim 6 , wherein the PCBA has a steady-state power density of approximately 130 W/in 2 to approximately 400 W/in 2 .
8. The PCBA of claim 6 , further comprising a power inverter module (PIM) for converting a DC link voltage into excitation waveform usable by the at least one joint motor.
9. The PCBA of claim 6 , further comprising sensor conditioning electronics (SCE) adapted for processing a set of signals describing at least a position of a motor of one of the motor-driven joints.
10. The PCBA of claim 6 , wherein the PCBA is collated with a corresponding one of the motor-driven joints.
11. The PCBA of claim 6 , wherein the PCBA includes a field-programmable gate array (FPGA) with a plurality of onboard processors each having a processing speed of at least 300 MHz.
12. The PCBA of claim 11 , wherein the PCBA is floating-point capable, and wherein the PCBA also includes at least 512 MB of non-volatile memory and at least 64 MB of volatile memory.
13. The PCBA of claim 6 , wherein the high-speed bus is a serialized bus configured for serializing a stream of output data, and for communicating the stream of data to the control circuit at the calibrated data transfer rate.
14. A robot comprising:
a plurality of joint motors;
a plurality of motor-driven joints each being driven by at least one of the joint motors; and
a control system having:
a top-level controller that generates task-based control input signals to command execution of a required task involving some of the joint motors;
a brainstem configured to process the task-based control signals to thereby determine which of the joints to activate to execute the required task, and to coordinate the motion of the activated joints; and
a joint-level controller in communication with the brainstem and having plurality of printed circuit board assemblies (PCBAs) each including a processor and a high-speed bus, the bus providing a calibrated data transfer rate between the PCBA and brainstem of less than approximately 1 KHz;
wherein each PCBA is configured to control a torque output of at least one of the joint motors and all degrees of freedom only of a corresponding one of the joints using a feedback control loop of at least approximately 10 KHz, and wherein the brainstem provides both Cartesian control and impedance-based control of the robot at the calibrated data transfer rate without also controlling the torque output.
15. The robot of claim 14 , further comprising a position sensor configured for determining a position of the motor as an analog signal, wherein each PCBA includes a converter chip that converts the analog signal to a digital signal, and that communicates the digital signal to the joint processor.
16. The robot of claim 14 , wherein each PCBA is positioned within the joint that is being controlled by the PCBA.
17. The robot of claim 14 , wherein the processor includes a field-programmable gate array (FPGA).
18. The control system of claim 1 , wherein the brainstem has a data output rate of less than approximately 400 Hz.
19. The robot of claim 14 , wherein the robot has at least 40 degrees of freedom (DOF), and wherein each PCBA controls all of the DOF of only one of the joints.