Multi-mode Transmission Torque Control via Closed-loop Speed Feedback
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Solution Overview
Problem
Powertrain systems with multi-mode transmissions face challenges in efficiently managing torque distribution and power transfer between torque actuators and the drivetrain, particularly when approaching power limits of power storage devices, leading to suboptimal tractive force and efficiency.
Innovation Solution
A closed-loop speed control system is employed to determine power limited torque commands for torque machines and engine torque commands, utilizing a multi-mode transmission with planetary gear sets and torque transmitting clutches to manage torque distribution, ensuring optimal tractive force and efficiency by switching between engine and torque machine operation modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If torque commands for torque machines are increased to maximize tractive force, then power demand from power storage device increases, but power storage device reaches power limit causing operational constraints
Solution Approach 1:
The control system dynamically adjusts torque commands for torque machines based on real-time power availability from the power storage device. When power demand approaches the power limit, the system reduces torque machine torque commands and compensates by increasing engine torque command, thereby maintaining tractive force while respecting power constraints.
Solution Approach 2:
The system changes operational parameters by switching between different torque sources (torque machines vs. engine) based on power availability. The control method modifies torque command parameters for torque machines and engine torque command parameters dynamically, transitioning from high torque machine operation to higher engine operation when power storage device limits are approached.
2Productivity
If multi-mode transmission operates in variable ratio modes to optimize torque distribution, then transmission complexity increases, but control precision and efficiency improve
Solution Approach 1:
The control system employs closed-loop feedback by continuously monitoring power demand, power storage device state, and transmission operating conditions. This feedback enables dynamic adjustment of torque commands and gear ratio selection, optimizing torque distribution efficiency while managing transmission complexity through adaptive control rather than fixed complex mechanisms.
Solution Approach 2:
The multi-mode transmission is designed to operate in multiple operational modes (fixed gear modes and variable ratio modes) that can be selectively engaged based on operating conditions. This multi-functionality allows the transmission to handle diverse torque distribution requirements while maintaining manageable complexity by using a unified control architecture that adapts to different modes.
3Power
If torque machines operate at high power output to maximize tractive force, then battery power limits are reached, but operating below power limits reduces available tractive force
Solution Approach 1:
The control system proactively monitors power storage device state and predicts when power limits will be approached. Before reaching the power limit, the system preemptively adjusts torque machine torque commands and transitions to engine-assisted operation, preventing power limit violations and maintaining reliable operation while maximizing torque machine power output within safe boundaries.
Data Source
AI summary
A powertrain including an engine and torque machines is configured to transfer torque through a multi-mode transmission to an output member. A method for controlling the powertrain includes employing a closed-loop speed control system to control torque commands for the torque machines in response to a desired input speed. Upon approaching a power limit of a power storage device transferring power to the torque machines, power limited torque commands are determined for the torque machines in response to the power limit and the closed-loop speed control system is employed to determine an engine torque command in response to the desired input speed and the power limited torque commands for the torque machines.