Electropermanent Magnet Motors for Low-Speed Torque
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Solution Overview
Problem
Existing micromotors and microactuators face challenges in providing efficient electromechanical energy conversion at high torque and low speed, especially at small dimensions, with conventional motors experiencing significant losses due to friction, magnetic demagnetization, and resistive heating, leading to low efficiency at low speeds and zero efficiency when stalled.
Innovation Solution
The use of electropermanent magnets in motors and actuators, where current pulses change the magnetization of the magnets, allowing for continuous motion and precise control of position or speed without continuous electrical power, reducing losses by minimizing current flow through windings and utilizing materials with different coercivity for efficient energy storage and conversion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If conventional permanent magnet motors are used, then continuous torque is produced, but resistive heating losses increase at low speeds and zero speed
Solution Approach 1:
The motor uses periodic pulsed current applied to electropermanent magnets to change their magnetization state, rather than continuous current. The electropermanent magnets are switched between magnetized and demagnetized states in pulses, producing torque only when needed, thereby eliminating continuous resistive heating losses at low or zero speeds.
Solution Approach 2:
The invention changes the magnetic parameter of the electropermanent magnets dynamically by applying current pulses that alter their magnetization state. This allows the motor to produce torque only when the magnets are in the appropriate magnetized state, rather than requiring continuous current flow, thus reducing energy losses.
2Force
If conventional permanent magnet motors operate at low speeds, then torque is maintained, but efficiency decreases due to continuous power consumption
Solution Approach 1:
The motor employs periodic pulsed current to switch electropermanent magnets between magnetized and demagnetized states, producing torque only during the pulsed intervals when needed. This eliminates continuous power consumption while maintaining torque at low speeds, significantly improving efficiency.
Solution Approach 2:
The electropermanent magnets maintain their magnetized state without continuous power input, using the applied current pulses only to change state when torque is needed. This self-holding capability allows the motor to maintain torque at low speeds without continuous power consumption.
3Loss of energy
If electropermanent magnets are used with pulsed current, then resistive heating losses are reduced, but continuous torque production becomes challenging
Solution Approach 1:
The motor uses periodic pulsed current to switch electropermanent magnets between magnetized and demagnetized states in a sequence that produces continuous torque. By carefully timing the pulses to multiple magnets around the rotor, continuous torque is achieved while maintaining low energy losses.
Solution Approach 2:
The motor divides the torque production task across multiple electropermanent magnets distributed around the rotor. By sequentially switching different magnets between magnetized and demagnetized states, continuous torque is produced through the segmented contribution of multiple magnets rather than requiring continuous current in a single magnet.
4Force
If speed-reducing power transmission is added to achieve high torque at low speed, then torque is increased, but device complexity and transmission losses increase
Solution Approach 1:
The invention replaces the need for mechanical speed-reducing transmissions with an electromagnetic approach using electropermanent magnets and pulsed current. The motor directly produces high torque at low speeds through controlled magnetization switching, eliminating complex mechanical transmission stages and associated losses.
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 enables high efficiency at low speeds and small dimensions, reducing resistive heating losses and maintaining efficiency even at zero speed, making it suitable for microrobotics and programmable matter applications.
Implementation Method 1
at least one coil that is wound around each electropermanent magnet and configured to pass current pulses that affect the magnetization of the magnet
Implementation Method 2
Passing current through (the coil of) these electropermanent magnets changes the magnetization of the materials inside, storing energy in the magnetic materials, changing the force they exert
Data Source
AI summary
An electropermanent linear actuator has a stator, forcer, drive circuitry, and feedback control mechanism. The stator includes at least one electropermanent magnet with a coil that passes current pulses that change the magnetization of the magnet, which change persists after current is removed. The forcer moves with respect to the stator in response to the persistent changes in magnetization. Drive circuitry controls the position or speed of the actuator by controlling the timing, magnitude, and/or shape of the current pulses. The voltage and duration of pulses are of sufficient magnitude to cause the magnetization change to persist after cessation of current, with voltage and current returning substantially to zero between pulses. The feedback control mechanism determines, based on actuator velocity or position, when the next current pulse should be issued, pulse issuance being timed so that the actuator will continue to move throughout the absence of applied current between pulses.