Electric Linear Actuator Torque Control for Low Power Consumption
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Solution Overview
Problem
Electric linear motion actuators used in brake systems experience high power consumption due to frictional losses in the motion conversion mechanism, which are undesirable and lead to energy inefficiency.
Innovation Solution
The system incorporates a motor control device that adjusts the electric current to the electric motor based on the hysteresis properties of the motion conversion mechanism, increasing torque until a predetermined pressing force is reached and then decreasing it, allowing for reduced power consumption by maintaining the pressing force at a target value with lower motor torque.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If constant electric current is applied to the electric motor to maintain pressing force, then the pressing force is maintained, but power consumption is high
Solution Approach 1:
The motor control device continuously monitors the pressing force via the load sensor and adjusts the electric current to the motor based on the detected pressing force magnitude, maintaining the target pressing force while optimizing power consumption through closed-loop control
Solution Approach 2:
The system dynamically changes the electric current parameter applied to the motor based on the detected pressing force, adjusting the current to match the actual load requirements rather than maintaining a constant high current, thereby reducing power consumption while maintaining reliability
2Loss of energy
If frictional forces in the motion conversion mechanism are reduced, then energy loss is reduced, but the hysteresis property cannot be utilized for power savings
Solution Approach 1:
The system converts the harmful hysteresis effect caused by friction into a beneficial feature by controlling the motor torque to decrease after reaching the target pressing force, utilizing the hysteresis loop to maintain pressing force with reduced torque and thereby reducing power consumption
Solution Approach 2:
The motor torque is controlled to periodically increase to a predetermined value and then decrease to maintain the pressing force, creating a cyclic torque pattern that exploits hysteresis to reduce average power consumption while maintaining continuous pressing force
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 effectively reduces the electric current required to maintain the pressing force, leading to lower power consumption and improved energy efficiency in the electric motor.
Implementation Method 1
large frictional forces occur in the motion conversion mechanism due to the reaction force which acts on the linear motion member from the target member
Implementation Method 2
the motion conversion mechanism comprises a mechanism showing a hysteresis property by which a magnitude of the torque of the electric motor when the pressing force is of any arbitrary magnitude while the torque is increasing is not identical to, but is larger than, a magnitude of the torque when the pressing force is of said arbitrary magnitude while the torque is decreasing
Data Source
Figure 1
Figure 2~3
Figure 4
AI summary
An electric linear motion actuator whose power consumption is low is provided. The electric linear motion actuator includes an electric motor (10), a motion conversion mechanism (11) for converting the torque of the electric motor (10) to the linear driving force of an outer ring member (24), a load sensor (12), and a motor control device (51). The motor control device (51) is configured to control the electric current applied to the electric motor such that the torque of the electric motor (10) increases until the pressing force detected by the load sensor (12) exceeds a target value, and then the torque of the electric motor (10) decreases until the pressing force detected by the load sensor (12) reaches the target value.