PI Controller Integrator Windup Detection for Vehicle Speed Control
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Solution Overview
Problem
Existing vehicle control systems face challenges in effectively minimizing driveline vibrations due to single-variable feedback control schemes, which can lead to inadequate vibration damping and integrator windup issues in hybrid vehicles with multiple prime movers.
Innovation Solution
A proportional-integral (PI) controller method that detects integrator windup and selectively freezes the integral torque control terms, allowing the proportional terms to saturate without affecting the speed control, thereby preventing further windup and maintaining control over the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the proportional torque saturates against a limit to provide maximum damping, then the damping torque is maximized, but the integral torque continues to wind up and accumulate error
Solution Approach 1:
The controller detects when the proportional torque saturates against a calibrated limit and preemptively freezes the integrator output to prevent windup before it occurs. This preliminary action maintains the damping torque at maximum while preventing the integral error from accumulating excessively.
Solution Approach 2:
The controller continuously monitors the proportional torque output and provides feedback to the integrator freeze/thaw logic. When saturation is detected, the feedback triggers the integrator freeze; when the proportional torque exits saturation, the feedback triggers the integrator thaw, creating a closed-loop prevention mechanism.
2Measurement precision
If the integrator is frozen to prevent windup, then integrator accuracy is maintained, but the system loses the ability to correct steady-state errors
Solution Approach 1:
The integrator freeze mechanism is dynamic rather than static. The controller continuously evaluates whether the proportional torque is saturated and adjusts the integrator state accordingly. When saturation occurs, the integrator is frozen; when saturation ends, the integrator is unfrozen and resumes correcting steady-state errors, allowing the system to adapt to changing operating conditions.
Solution Approach 2:
The system uses feedback from the proportional torque saturation status to control the integrator freeze/thaw state. This feedback mechanism ensures the integrator is only frozen when necessary (during saturation) and is unfrozen when normal operation resumes, maintaining both accuracy and error correction capability.
3Device complexity
If single-variable feedback control is used to simplify control, then controller complexity is reduced, but vibration damping performance becomes inadequate
Solution Approach 1:
The controller merges speed control and damping torque control into a single integrated PI controller. The proportional term handles damping torque while the integral term handles speed control, combining both functions in one controller structure. This reduces overall system complexity compared to separate controllers while providing adequate vibration damping through the proportional term and speed control through the integral term.
Data Source
AI summary
A method or algorithm controls a motor in a vehicle having a proportional-integral controller. The controller determines a commanded damping control torque as a proportional output torque value and a commanded motor speed control torque as an integrator output torque value. The integrator torque output value is frozen only if the proportional torque output value saturates against a limit and the direction of the speed error is the same as that of the integrator torque output value. The proportional torque output value is calculated using different error values than are used in calculating the integrator output value. A vehicle includes one or more traction motors and the controller noted above. For two motors, the controller determines the damping torques and motor speed control torques separately for each motor.