Servomotor Control Device Inertia Ratio Gain Adjustment
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Solution Overview
Problem
Existing servomotor control systems face limitations in raising responsiveness in velocity control loops due to delays, which restrict the increase of integral gain when proportional gain is increased, especially in multi-rate systems with different calculation cycles for integral and proportional terms.
Innovation Solution
A servomotor control device and method that adjusts the integral and proportional gains based on the ratio of total machine inertia to rotor inertia, with the integral gain set to a value smaller than the square of the velocity gain magnification according to delay time, and the proportional gain adjusted by the difference in calculation cycles, allowing for higher responsiveness without compromising damping characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the integral gain is increased by the square of the proportional gain magnification to increase responsiveness, then the responsiveness is improved, but the velocity gain is limited at the boundary due to delay time in the velocity control loop
Solution Approach 1:
The patent changes the parameter relationship from integral gain = (proportional gain magnification)² to integral gain = (proportional gain magnification)^(2-γτ), where γ is a positive constant and τ is the delay time. This parameter modification allows the integral gain to account for delay effects, enabling higher velocity gain magnification while maintaining stability in the presence of delays in the velocity control loop.
Solution Approach 2:
The patent introduces a dynamic adjustment mechanism where the exponent of the integral gain relationship is modified based on the delay time characteristics of the system. This dynamic approach allows the control system to adapt to the presence of delays, enabling higher responsiveness while preventing oscillatory overshoot that would occur with fixed gain relationships.
2Device complexity
If the calculation cycle for the integral term is made longer to reduce computation load, then the device complexity is reduced, but the responsiveness of the velocity control loop deteriorates
Solution Approach 1:
The patent segments the velocity control loop into two different calculation cycles: a first calculation cycle for the proportional term and a second calculation cycle for the integral term. This segmentation allows the proportional term to be calculated more frequently for high responsiveness, while the integral term is calculated less frequently to reduce computation load, with the modified gain relationship compensating for the slower integral update rate.
3Speed
If the proportional gain magnification is increased to improve responsiveness, then the responsiveness is improved, but oscillatory overshoot occurs due to delay time in the velocity control loop
Solution Approach 1:
The patent modifies the parameter relationship between integral gain and proportional gain magnification from a fixed square relationship to a delay-compensated relationship with exponent (2-γτ). This parameter change allows higher proportional gain magnification to be applied without causing oscillatory overshoot, as the integral gain is adjusted to account for the delay time, thereby maintaining damping characteristics even with increased responsiveness.
Solution Approach 2:
The patent applies preliminary anti-action by pre-calculating the delay-compensated gain relationship before implementing the control. The exponent (2-γτ) is determined based on the known delay time characteristics, allowing the integral gain to be set in advance to counteract the destabilizing effects of delay, preventing oscillatory overshoot before it occurs.
Data Source
AI summary
A servomotor control device includes a torque command creation part for creating a torque command value for driving a servomotor. The torque command creation part includes a proportional gain part and an integral gain part. An integral gain is set as a value calculated by multiplying an initial value, by a ratio J/Jm of total inertia of a machine relative to rotor inertia of the servomotor, and a value set smaller than the square of a velocity gain magnification according to delay time of the velocity control loop. A proportional gain is a value calculated by adding a value according to a difference in calculation cycle between the integral term and the proportional term, and the integral gain, to a value calculated by multiplying an initial value by the ratio J/Jm and the velocity gain magnification.