Motor Controller Backlash Suppression via Integral Sharing
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Solution Overview
Problem
Existing motor controllers using tandem control to drive large or unstable driven bodies with significant backlash between motors face challenges in suppressing backlash due to mechanical shocks and accumulation of preload torque, which renders conventional methods ineffective.
Innovation Solution
A motor controller system with two motors, a position detector, and a velocity detector, utilizing a control system that computes velocity and torque commands, and includes a compensation unit to add preload torque gradually based on a time constant, and an integral element sharing mechanism to maintain identical output values across motors, preventing backlash and mechanical shocks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If preload torque is added to suppress backlash, then backlash suppression is improved, but mechanical shocks occur during addition or removal of preload torque
Solution Approach 1:
The patent applies preliminary action by gradually increasing the preload torque from zero to the target value before actual operation, and gradually decreasing it afterward. This gradual transition prevents sudden mechanical shocks that would occur with immediate full preload application, while still achieving effective backlash suppression during the operational phase.
2Reliability
If preload torque is added in position tandem control, then backlash suppression is improved, but the reciprocal of preload torque accumulates in velocity integrator causing output torque to become zero
Solution Approach 1:
The patent applies preliminary action by establishing velocity integrator sharing before adding preload torque. By making the velocity integrator outputs identical in advance, the system creates a balanced state where subsequent preload torque addition does not cause unbalanced accumulation that would drive output torque to zero.
Solution Approach 2:
The patent merges the velocity integrator outputs of the two motors by making them identical through sharing. This merging ensures that when preload torque is added, both motors experience the same integral accumulation, preventing the imbalance that would otherwise cause output torque to become zero while maintaining backlash suppression.
3Stability of the object's composition
If velocity integrator outputs are made identical, then torque balance is improved, but device complexity increases due to integral element sharing means
Solution Approach 1:
The patent merges the velocity integrator functions by making the outputs identical through sharing. This consolidation approach achieves torque balance between the two motors while adding minimal complexity compared to implementing completely independent control systems for each motor.
Data Source
AI summary
In position tandem control in which one movable member is driven by two motors, an output of the integral element of the velocity control unit in the control system for one motor is copied to the integral element of the velocity control unit in the control system for the other motor. A preload is added to a torque command output from each of the velocity control units in the motor control systems for two motors so that torques in mutually opposite directions are generated to suppress backlash between gears.