Servomotor Control Device Switching Force Estimation for Oscillation Suppression
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Solution Overview
Problem
Servomotor control devices experience oscillation in position compensation during stop or low-speed operations due to compensation reacting to estimated drive forces unrelated to mechanical operation, leading to precision issues in position control of driven bodies.
Innovation Solution
A servomotor control device that switches between a first and second force estimated value, with the second value being a fixed value determined in advance, to compensate the position command value, especially during low-speed or rapid traverse operations, and applies filtering and integrator overwriting to prevent discontinuity in compensation amounts.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If position compensation is applied based on estimated drive force during stop or low-speed operation, then position control precision is improved, but oscillation of compensation amount arises
Solution Approach 1:
The patent dynamically switches between two different force estimation methods based on the command speed. When command speed exceeds a threshold, the system uses the first force estimation method (based on torque command and efficiency). When command speed is at or below the threshold, it switches to the second force estimation method (based on friction model). This dynamic adaptation resolves the contradiction by applying the appropriate estimation method for each operational state, preventing oscillation during low-speed operations while maintaining precision during high-speed operations.
Solution Approach 2:
The patent changes the parameter used for force estimation based on the command speed threshold. Above the threshold, it uses torque command value and motor efficiency parameters. At or below the threshold, it switches to using friction coefficients and normal force parameters. This parameter change strategy allows the system to avoid using torque-based estimation during low-speed operations where it causes oscillation, while maintaining accurate compensation during high-speed operations.
2Measurement precision
If torque command value is used to estimate drive force during high-speed operation, then position compensation accuracy is improved, but oscillation occurs during low-speed operation
Solution Approach 1:
The system dynamically selects the force estimation method based on command speed. During high-speed operation (above threshold), it uses the torque command value-based estimation which provides accurate position compensation. During low-speed operation (at or below threshold), it switches to the friction model-based estimation which provides reliable, oscillation-free compensation. This dynamic selection ensures both accuracy and reliability across different operational states.
Solution Approach 2:
The patent changes the estimation parameters based on operational speed. For high-speed operations, it uses torque command value and motor efficiency as parameters. For low-speed operations, it switches to using friction coefficients (μ1, μ2) and normal force parameters. This parameter adaptation ensures reliable compensation by avoiding the oscillation-prone torque-based method during low-speed operations while maintaining accuracy during high-speed operations.
Data Source
AI summary
A servomotor control device includes a connection mechanism configured to connect a servomotor and a driven body, and transmit power of the servomotor to the driven body, a position command generation unit configured to generate a position command value for the driven body, a motor control unit configured to control the servomotor using the position command value, a force estimation part configured to estimate drive force acting on the driven body at a connecting part with the connection mechanism, a switching part configured to switch between a first force estimated value estimated by the force estimation part and a second force estimated value that is a fixed value, and a compensation amount generation part configured to generate a compensation amount for compensating the position command value generated by the position command generation part, based on the first or second force estimated value that was switched to by the switching part.