EV Clutch Control for Variable-Magnetism Motor Torque Shock
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Solution Overview
Problem
Existing control systems for electric vehicles with variable magnetism magnets in the rotor experience torque shocks due to friction coefficient differences during clutch engagement, leading to driver discomfort and potential clutch damage from sudden speed rises.
Innovation Solution
A control device that performs torque and clutch control to match engaging torque with demanded torque, transitions the clutch to a micro slip state by adding a slip torque based on friction coefficients, and adjusts hydraulic pressure to stabilize the system during magnetism changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the clutch is made to slip to suppress torque shock during magnetization, then torque shock is reduced, but sudden speed rise occurs which may damage the clutch with frictional heat
Solution Approach 1:
The control device performs preliminary action by switching from torque control to power control before the magnetization process begins. This anticipatory control change prevents sudden speed rise by establishing power control as the governing mechanism before high torque is applied during magnetization, thereby eliminating the harmful effect while maintaining clutch slip for torque shock suppression.
Solution Approach 2:
The control device applies dynamics by dynamically switching between two control modes (torque control and power control) based on the operational phase. During magnetization, power control is activated to dynamically manage both torque and rotational speed, allowing the system to adapt to changing conditions and prevent sudden speed rise while maintaining the necessary clutch slip condition.
2Manufacturing precision
If a large d-axis current is applied for magnetization, then magnetism changes to the optimum value, but it interferes with the q-axis current for torque generation
Solution Approach 1:
The control device applies periodic action by implementing sequential control phases: first applying d-axis current for magnetization, then switching to q-axis current for torque generation. This time-separated approach ensures that magnetization and torque generation do not occur simultaneously, eliminating the interference between d-axis and q-axis currents while achieving both objectives in sequence.
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
The control device effectively suppresses torque variations and shocks during magnetism changes, stabilizing the clutch and preventing damage by anticipating friction coefficient differences, ensuring smooth operation.
Implementation Method 1
a phenomenon in which rotation of the drive motor increases rapidly (so-called 'sudden speed rise') occurs. Such a phenomenon of the sudden speed rise may damage the clutch with frictional heat caused by the slip
Data Source
AI summary
A control device for an electric vehicle is provided, which includes a drive motor of which magnetic poles of a rotor are comprised of variable magnetism magnets, and a clutch disposed between the drive motor and driving wheels. When the electric vehicle travels, the control device performs a torque control, and a first clutch control in which an engaging torque of the clutch is controlled to be higher than a demanded torque. When performing a magnetization control when the electric vehicle travels, the control device changes the clutch control from the first clutch control to a second clutch control in which the engaging torque is made to coincide with the demanded torque, before the execution of the magnetization control, and adds a given slip torque to the demanded torque to start a micro slip control in which the clutch is transitioned from an engaged state into a micro slip state.