Seat Pneumatic Pump PWM Control to Avoid Switch-On Current Peaks
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Solution Overview
Problem
The service life of pumps used in motor vehicle seat systems is impaired due to high switch-on currents resulting from pulse width modulation (PWM) control of fluid actuators, leading to frequent switch-on cycles.
Innovation Solution
A method is introduced where the duty cycle of the PWM signal for the electric motor is adjusted to a working level during filling phases and lowered to a lower level between phases, ensuring the rotor continues to rotate, thereby avoiding high switch-on currents and maintaining pump operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the pump is switched on and off frequently to fill fluid actuators in temporal succession, then the fluid actuators can be filled and emptied as required for massage functions, but the service life of the pump is impaired due to high switch-on currents
Solution Approach 1:
The pump is kept in a preliminary ready state by maintaining a low PWM duty cycle between filling phases, so that when a filling phase begins, the pump can immediately operate at working level without requiring a full switch-on cycle. This preliminary preparation eliminates the harmful switch-on current peaks while maintaining the ability to fill actuators on demand.
Solution Approach 2:
The PWM duty cycle is dynamically adjusted between two states: a working level during filling phases and a lower level between phases. This dynamic adjustment allows the pump to remain operational without complete shutdown, transforming the static on/off switching into a continuous dynamic operation that avoids the harmful effects of frequent switch-on cycles.
2Loss of energy
If the PWM duty cycle is lowered to zero between filling phases to save energy, then energy consumption is reduced, but the pump stops rotating and generates high switch-on currents during the next filling phase
Solution Approach 1:
Instead of completely stopping the pump (100% duty cycle reduction), the invention applies a partial action by maintaining a low but non-zero PWM duty cycle between filling phases. This partial operation consumes minimal energy while keeping the pump rotor rotating, thereby avoiding the excessive switch-on currents that would result from complete shutdown and subsequent restart.
3Ease of operation
If the pump operates continuously at working level PWM duty cycle, then the pump is always ready to fill fluid actuators, but energy is wasted during periods when no filling is required
Solution Approach 1:
The PWM duty cycle is varied periodically according to the actual operational requirements: high (working level) during filling phases when fluid actuation is needed, and low (but non-zero) during intervals between phases when no filling is required. This periodic modulation optimizes the balance between pump readiness and energy consumption, avoiding both continuous full-power operation and complete shutdown.
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 extends the service life of the pump by preventing high switch-on currents, protecting the pump and allowing it to operate continuously without additional components, while maintaining efficient fluid actuation.
Implementation Method 1
The motor of the pump is an electric motor controlled by a PWM signal
Implementation Method 2
the duty cycle of the PWM signal applied to the electric motor of the pump is set to a working level during a filling phase and is lowered to a level lower than the working level between the filling phases
Data Source
AI summary
A method for actuating a fluid actuator in a motor vehicle seat system having a motor vehicle seat and a pneumatic system for actuating a seat function. The pneumatic system has a pump and the fluid actuator housed in the motor vehicle seat. The pump motor is an electric motor controlled by a PWM signal and is set up to fill the fluid actuator with fluid within a filling phase. The pneumatic system is set up to withdraw fluid from a fluid actuator filled with fluid, in an emptying phase. The fluid actuator runs through a plurality of filling phases and emptying phases in succession. The duty cycle of the PWM signal is set to a working level during a filling phase and is lowered to a lower level between filling phases. The lower level is dimensioned such that the rotor of the pump motor can still rotate.