Dynamometer Torque Control via Feedforward Segmentation
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Solution Overview
Problem
Conventional dynamometer systems struggle to stably control torque fluctuation at frequencies higher than their control band, leading to insufficient responsiveness and potential instability due to limitations in feedback gain adjustments.
Innovation Solution
A dynamometer system incorporating an excitation torque command calculation unit, feedback controller, feedforward input calculation unit, and control input addition unit to calculate and superimpose alternating-current components, allowing for stable torque control beyond the control band by adjusting the excitation torque command value and amplitude to match the commanded frequency and amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the feedback gain of the shaft torque controller is increased to improve responsiveness at high frequencies, then the response characteristics improve, but the control system becomes unstable depending on operating conditions
Solution Approach 1:
The torque control is segmented into two independent control loops: a feedback controller for low-frequency torque control and a feedforward controller for high-frequency excitation torque control. This segmentation allows each controller to operate within its optimal frequency range, preventing the stability issues that would arise from using high feedback gain across all frequencies.
Solution Approach 2:
The system changes the control approach based on frequency parameters. For frequencies above the predetermined threshold, the feedforward controller takes over with predetermined gain values, while the feedback controller handles lower frequencies. This parameter-based switching resolves the contradiction by adapting the control strategy to the specific frequency requirements.
2Reliability
If the feedback gain is excessively increased to improve high-frequency response, then the responsiveness improves, but the control system becomes unstable
Solution Approach 1:
The control system is divided into feedback and feedforward segments, each responsible for specific frequency ranges. The feedforward controller handles high-frequency excitation with predetermined gains, ensuring reliable torque control without compromising system stability.
Solution Approach 2:
The feedforward controller acts as an intermediary that handles high-frequency torque control independently, preventing the need to increase feedback gain excessively. This intermediary controller ensures both reliability and stability by operating within predetermined gain limits.
3Power
If conventional feedback control is used for high-frequency torque fluctuation, then the control band is limited to several dozen Hz, but the responsiveness becomes insufficient
Solution Approach 1:
The control system segments frequency responsibilities: the feedback controller manages low-frequency torque control within its stable band, while the feedforward controller handles high-frequency excitation torque. This segmentation extends the effective control authority to higher frequencies without sacrificing the stability of the feedback loop.
Solution Approach 2:
The feedforward controller performs preliminary action by pre-calculating the excitation torque command based on the excitation frequency and amplitude commands. This preliminary calculation allows the system to respond quickly to high-frequency torque fluctuations without waiting for feedback, thereby improving response speed while maintaining control authority.
Data Source
AI summary
Provided is a test system capable of stable torque control. A test system is provided with: an excitation torque command calculation unit which calculates an excitation torque command value; a shaft torque command calculation unit which defines a value obtained by adding up a base torque command value and the excitation torque command value as a torque command value; a controller which determines a first control input value such that a shaft torque detection value becomes the shaft torque command value; a feedforward input calculation unit which defines a value obtained by removing components equal to or less than a predetermined frequency from the shaft torque command value as a second control input value; and an addition unit which defines a value obtained by adding up the first and second control input values as a torque current command value.