Hybrid Powertrain Clutch Modulation for Motor Stall Prevention
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Solution Overview
Problem
Work vehicles with hybrid powertrains face challenges in maintaining electric motor torque capability when the motor speed approaches or falls below the stall speed, leading to potential derating and efficiency issues, especially in high torque, low speed applications.
Innovation Solution
A power control system with a controller that monitors electric motor speed and implements clutch modulation by partially engaging clutches in the transmission, preventing motor stall by maintaining speeds above the stall speed threshold, thereby ensuring consistent torque delivery without the need for larger motors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the electric motor operates in high torque, low speed applications, then the motor can provide sufficient force for work vehicle tasks, but the motor speed approaches or falls below the stall speed threshold causing torque derating and efficiency loss
Solution Approach 1:
The clutch engagement state is dynamically adjusted based on real-time motor speed monitoring. When motor speed approaches the stall threshold, the clutch is modulated to a partially engaged state, creating a flexible, adaptive connection that allows the motor to operate above stall speed while still delivering high torque to the load.
Solution Approach 2:
The system changes the operational parameters of the clutch by transitioning from a binary engaged/disengaged state to a continuous partially engaged state. This parameter change allows precise control over the torque transmission ratio, enabling the motor to maintain optimal speed-torque operating points.
2Power
If the clutch is fully engaged to transfer maximum power from the electric motor, then the motor torque is effectively delivered to the load, but the motor speed drops below the stall speed threshold causing derating
Solution Approach 1:
Instead of fully engaging the clutch, the system applies partial engagement to achieve the necessary power transfer without over-constraining the motor. This partial action allows the motor to maintain higher speed above the stall threshold while still delivering sufficient torque to the load through the partially engaged clutch.
Solution Approach 2:
The control system continuously monitors motor speed and uses this feedback to adjust the clutch engagement state. When motor speed approaches the stall threshold, the feedback loop triggers clutch modulation to reduce the load on the motor, maintaining speed above the critical threshold while preserving power transfer capability.
3Speed
If the clutch is disengaged to allow the electric motor to maintain higher speed above stall threshold, then motor torque capability is preserved, but power transfer to the load is reduced
Solution Approach 1:
The clutch serves as an intermediary element between the electric motor and the load. By controlling the clutch's partial engagement, it mediates the torque transmission, allowing the motor to operate at higher speeds while still delivering adequate power to the load through the intermediate clutch connection.
Data Source
AI summary
A control system for a work vehicle includes a power source including an engine and at least one electric motor configured to generate power; a transmission including a plurality of clutches coupled together and configured for selective engagement to transfer the power from the engine and the at least one electric motor along a power flow path to drive an output shaft of a powertrain according to a plurality of transmission modes; and a controller coupled to the power source and the transmission. The controller has a processor and memory architecture configured to: monitor an electric motor speed of the at least one electric motor; and generate and execute, when the electric motor speed is less than a first predetermined stall speed threshold, a clutch modulation command for the transmission such that at least one clutch of the plurality of clutches along the power flow path is partially engaged.