Steering Control Guard Circuit for Torque Assist Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing steering control apparatuses fail to maintain assist control when a current command value is abnormal due to systematic errors, leading to inadequate torque control by synchronous motors.
Innovation Solution
A steering control apparatus with a guard processing circuit that prevents excessive reduction in current command values, ensuring sufficient torque assist by maintaining a minimum current level even when systematic errors occur, and adjusts current values based on temperature and vehicle speed thresholds.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the current command value is reduced to facilitate convergence of the phase-control angle, then the control gain is reduced and convergence is improved, but the torque generated by the synchronous motor becomes insufficient and assist control cannot be carried out
Solution Approach 1:
The guard processing circuit performs preliminary protection by preventing the current command value from being reduced below a predetermined threshold before the reduction can cause loss of assist control. This advance guard ensures that the current command value maintains sufficient magnitude for torque generation while still allowing controlled reduction for convergence.
Solution Approach 2:
The guard processing circuit acts as an intermediary between the command value setting circuit and the current control circuit. It mediates the current command value by imposing a lower limit constraint, allowing the system to benefit from reduced control gain while preventing excessive reduction that would compromise torque generation capability.
2Reliability
If the current command value is excessively small due to systematic error, then the γ axis current decreases, but the variation in torque caused by manipulation of the phase-control angle is reduced making it impossible to suitably control the torque
Solution Approach 1:
The guard processing circuit applies preliminary anti-action by counteracting the systematic error that causes excessive reduction of the current command value. By preventing the current command value from falling below the predetermined threshold, it compensates for the systematic error before it can eliminate torque control capability.
Solution Approach 2:
The system uses feedback control where the phase-control angle manipulating circuit manipulates the phase-control angle based on the difference between detection value and target torque. The guard processing circuit ensures this feedback mechanism remains effective by maintaining the current command value above the threshold necessary for torque variation.
Data Source
Figure 1
Figure 2
Figure 3
AI summary
Using an update amount (Δθc), an update amount calculating circuit (M54) manipulates a phase-control angle (θc) so as to perform feedback control such that a steering torque (Trqsl) corresponds to a target torque (Trqs*). The steering torque (Trqsl) is obtained by reducing a steering torque (Trqs) in magnitude by a predetermined value (TrqL2). The phase-control angle (θc) is used to convert a current command value (iγ*) to a value of a fixed coordinate system, for example. Using a guard value, a guard processing circuit (M60) performs a guard process on a current command value (iγ1*) set by a command value setting circuit (M24), so that the current command value (iγ1*) becomes the current command value (iγ*). The guard value is used to determine an appropriate range for a variation in the current command value (iγ*) in accordance with an amount by which the steering torque (Trqs) exceeds in magnitude the target torque (Trqs*).