Robot Joint Torque Control With Load Compensation Feedback
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Solution Overview
Problem
Current robot joint torque control systems face instability due to excessive control parameter settings in PD control, which leads to system instability, and are limited by the influence of load parameters on actual torque output.
Innovation Solution
A load compensation method is introduced, where a load compensation controller accumulates a current if whose joint-end velocity is compensated, and this current is used as a current loop input instruction to mitigate the influence of load parameters on torque output. The controller design includes a reduction ratio, velocity feedback coefficient, and current loop control parameters to enhance system stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If PD control parameters are set excessively large to achieve better control performance, then control performance is improved, but system stability deteriorates
Solution Approach 1:
The patent introduces a load compensation controller that uses feedback from the actual torque sensor to calculate and compensate for the influence of load parameters. The controller computes a compensation current based on the ratio of actual torque to nominal torque, which is then added to the PD control output. This feedback mechanism allows the system to maintain stability while achieving better control performance by dynamically adjusting for load variations.
Solution Approach 2:
The patent changes the control parameters by introducing a load compensation term that dynamically adjusts the control output based on actual load conditions. The compensation current if is calculated as if = (Tp/Tnom-1)×irn, where Tp is actual torque and Tnom is nominal torque. This parameter change allows the system to adapt to varying load conditions without requiring excessively large PD control parameters, thereby maintaining system stability.
2Ease of operation
If PD control is used alone for simplicity, then ease of operation is improved, but control performance deteriorates due to load parameter influence
Solution Approach 1:
The patent merges PD control with load compensation control into a unified control system. The total control current is the sum of PD control current and load compensation current: i = if + ir. This combination maintains the simplicity of PD control while adding load compensation to improve performance. The merged approach preserves ease of implementation while eliminating the limitation of load parameter influence.
Solution Approach 2:
The load compensation controller automatically adjusts the control output based on the actual load conditions detected by the torque sensor. The system self-regulates by computing the compensation current based on the ratio of actual torque to nominal torque, eliminating the need for complex manual tuning or external intervention. This self-service mechanism improves control performance while maintaining operational simplicity.
3Measurement precision
If advanced control methods like quantitative feedback control or robust control are used to achieve desirable control effect, then control performance is improved, but device complexity increases
Solution Approach 1:
The patent extracts only the essential load compensation function from complex control theories, isolating the specific mechanism needed to counteract load parameter influence. Instead of implementing full quantitative feedback control or robust control systems with complex models, the invention extracts and applies only the load compensation term if = (Tp/Tnom-1)×irn. This extraction achieves desirable control effect while avoiding the complexity of comprehensive advanced control implementations.
Data Source
AI summary
A robot joint torque control system and a load compensation method therefor are provided, which relate to the technical field of robot joint motion control. A mathematical model of the robot joint torque control system is established first. Equivalent transformation is performed on a system functional block diagram thereof, and then it can be seen that load parameters have a great influence on joint torque output. A load compensation controller is designed to effectively eliminate the influence of the load parameters on an output torque of the joint. The system is equivalent to an inertial element on the basis of the compensation, and then a PD controller parameter is adjusted to increase an open-loop gain of the system, so as to increase a system bandwidth and increase a response speed of the joint torque control system, thereby improving performance of the joint torque control system.