Electric Motor Spin-Up Control for Neutral Driveline Reconnection
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Solution Overview
Problem
Conventional electric motor spin up and reconnection techniques in electrified vehicles are inadequate for quickly and precisely synchronizing motor and vehicle speeds during reconnecting, due to communication delays and differing system dynamics.
Innovation Solution
A control system that commands open-loop torque to overcome static friction, followed by feed-forward target speed with an offset to compensate for delays, and transitions to closed-loop control for precise synchronization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional spin up control methods are used, then the electric motor can be reconnected to the driveline, but the synchronization process is slow and imprecise due to communication delays and static friction dynamics
Solution Approach 1:
The control system applies open-loop torque commands before reconnection to pre-spin the motor shaft and overcome static friction, preparing the motor for rapid synchronization upon reconnection. This preliminary action eliminates the need for slow gradual spin-up during the actual reconnection process.
Solution Approach 2:
The patent replaces traditional mechanical friction-based torque transmission with an electrical control system that uses feed-forward torque commands and dynamic friction models to predict and compensate for friction effects, enabling faster and more precise motor spin-up control.
2Speed
If open-loop torque control is applied to overcome static friction, then the motor can begin spinning faster, but communication and actuation delays cause speed synchronization errors
Solution Approach 1:
The control system uses feedback from motor speed sensors to continuously monitor actual motor speed and compares it with the target speed. This feedback is used to adjust subsequent torque commands and compensate for delays in the control loop, maintaining synchronization accuracy despite communication and actuation delays.
Solution Approach 2:
The system calculates and applies feed-forward torque commands in advance, accounting for known communication delays and static friction characteristics. This preliminary calculation ensures that the motor reaches the desired speed profile despite delays in signal transmission and actuator response.
3Loss of energy
If the electric motor remains connected to the driveline, then speed synchronization is maintained, but system losses increase due to continuous torque requirements
Solution Approach 1:
The control system performs rapid preliminary spin-up actions using open-loop torque commands before reconnection, enabling the motor to quickly synchronize with driveline speed upon reconnection. This allows the motor to remain disconnected longer (reducing losses) while ensuring smooth reconnection when needed.
Solution Approach 2:
The system uses periodic control updates with feed-forward torque commands that account for the periodic nature of friction dynamics and motor acceleration. This periodic control approach maintains synchronization accuracy while allowing the motor to remain disconnected during periods when torque is not required.
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
Facilitates faster and smoother electric motor spin up and reconnection, enhancing vehicle efficiency and driver experience.
Implementation Method 1
commanding the electric motor to generate an open-loop torque in an attempt to overcome a static friction of the electric motor and to begin spinning the electric motor
Data Source
AI summary
A modeling and control technique for an electric motor of an electrified vehicle includes preparing for reconnection of an electric motor to a driveline, which were temporarily disconnected by a disconnect system therebetween, by commanding the electric motor to generate an open-loop torque in an attempt to overcome a static friction of the electric motor and to begin spinning the electric motor, receiving a set of operating parameters of the electrified vehicle including (i) a speed of the electrified vehicle and (ii) a speed of the electric motor, and in response to detecting that a speed/position of the electric motor increases to the value greater than zero, commanding a feed-forward target speed for open-loop control of the electric motor, wherein the feed-forward target speed ignores static friction dynamics and is offset by a first offset to compensate for delay in actuating the electric motor.