Power Seat Positioning Control for Rotation Sensor Backlash
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Solution Overview
Problem
Existing positioning devices for electric power seats in vehicles suffer from inaccurate positioning due to erroneous detection of the movable position by rotation sensors, caused by factors such as short operations, external forces, and backlash, leading to significant deviations in seat positions during memory power seat reproduction.
Innovation Solution
The positioning device employs deceleration control mechanisms, including inertial, braking, and forced braking modes, to stop the DC motor at a target rotation stop position midway between the rising and falling edges of the rotation sensor pulses, using variable voltage and current control to ensure accurate positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the motor stops at the edge of the pulse output by the rotation sensor, then the positioning is simpler, but erroneous detection occurs due to external forces and backlash causing the motor to rotate slightly after stopping
Solution Approach 1:
The system performs preliminary deceleration control before the motor reaches the target position, stopping the motor at a predetermined distance from the pulse edge. This advance action prevents the motor from stopping too close to the critical zone where external forces and backlash could cause erroneous pulse detection, thereby resolving the contradiction between simple positioning and accurate measurement.
2Productivity
If the motor operates at high speed for productivity, then the positioning response is faster, but the rotation sensor may miss pulses due to the motor stopping before generating a pulse
Solution Approach 1:
The system continuously monitors the motor's rotational position through the rotation sensor and implements feedback control. By detecting the motor's actual position and comparing it with the target position, the system can adjust the stopping point to ensure it does not coincide with pulse edges, even during high-speed operation. This feedback mechanism maintains both high productivity and accurate pulse detection.
3Loss of time
If the motor is stopped immediately upon reaching the target position, then the control time is shorter, but the motor may rotate due to backlash in the speed reduction mechanism
Solution Approach 1:
The system performs preliminary deceleration before the motor reaches the target position, creating a buffer zone that accounts for potential backlash-induced rotation. By stopping the motor at a predetermined distance from the target, the system ensures position stability without requiring additional compensation time, thus resolving the contradiction between control time and position stability.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach prevents erroneous pulse generation and maintains accurate seat positioning, even after multiple repetitions, by decelerating the motor to a precise stop position, reducing deviations and ensuring consistent reproduction of set seat positions.
Implementation Method 1
a Hall element 202 arranged in a fixed portion to detect the magnetic field generated by the magnet as an electric signal
Implementation Method 2
an actuator composed of a DC motor, a speed reduction mechanism
Data Source
AI summary
A positioning device contains an actuator composed of a DC motor, a deceleration mechanism, and a single-phase rotation sensor for detecting the amount of rotational displacement of the deceleration mechanism, and an electronic control unit that electrically drives the DC motor. The electronic control unit decelerates and controls the DC motor to stop at a target rotation stop position, which is approximately midway between the rising edge and the falling edge of the output pulse of the rotation sensor.