Gear Shift Synchronization Torque Control for Parallel-Shaft Gearboxes
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Solution Overview
Problem
Existing methods for synchronizing gearshifts in vehicles with parallel-shaft gearboxes without synchronization mechanisms face challenges in minimizing torque surges, particularly during heavy braking on steep gradients, leading to poor wear of mechanical parts and a non-transparent coupling experience for the driver.
Innovation Solution
A method that calculates a torque command to minimize the speed difference between primary and secondary shafts by constructing an intermediate torque signal, taking into account the energy supplied to the system, to synchronize the shafts quickly and smoothly, avoiding excessive torque surges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the torque of the electric traction machine is maintained at a high constant value until the speed difference is reduced below a threshold, then the coupling smoothness is improved, but the synchronization time is extended due to the inertia of the traction unit
Solution Approach 1:
The patent applies dynamics by making the torque command dynamic rather than static. The torque command evolves through different phases: initially constant to maintain coupling smoothness, then proportional to the speed difference to accelerate synchronization when the threshold is reached. This dynamic adjustment resolves the contradiction by adapting the torque profile to the real-time synchronization state.
Solution Approach 2:
The patent implements periodic action through the two-phase torque control strategy. Phase 1 uses constant torque for a predetermined time or until a speed difference threshold is reached, then Phase 2 activates with proportional torque control. This periodic switching between control modes optimizes both coupling smoothness and synchronization speed.
2Power
If the engine speed difference occurs very rapidly within a range of 30 revolutions per minute, then the required torque at the wheel is maintained, but torque surges occur during coupling causing uneven wear on mechanical components
Solution Approach 1:
The patent applies preliminary action by pre-calculating and applying a specific torque command profile before the coupling event. The controller prepares the traction machine with an optimal torque trajectory that anticipates the coupling requirements, ensuring the speed difference reaches the acceptable threshold quickly but smoothly, preventing torque surges during the actual coupling moment.
Solution Approach 2:
The patent uses feedback by continuously monitoring the speed difference between the primary shaft and pinion, and adjusting the torque command based on this feedback. The proportional relationship between torque command and speed difference creates a closed-loop control system that automatically regulates torque to minimize speed differential without causing surges, while maintaining required wheel torque through appropriate gain selection.
3Measurement precision
If a torque command is sent to the traction machine to minimize the speed difference, then the synchronization accuracy is improved, but the coupling transparency to the driver deteriorates due to the inertia and response time of the traction unit
Solution Approach 1:
The patent applies parameter changes by systematically varying the torque command parameters through the two-phase control strategy. Phase 1 uses a high constant torque parameter to overcome inertia quickly, then Phase 2 transitions to a proportional parameter relationship that fine-tunes the synchronization. This parameter evolution achieves high synchronization accuracy while the rapid initial response maintains coupling transparency by completing the process before the driver can perceive delays.
Data Source
Figure 1A~1C
Figure 2
AI summary
Method for controlling the synchronization of a pinion (6) rotating on a primary shaft driven by a traction machine of the vehicle and rotationally connected to a secondary shaft of a parallel shaft gearbox that has no synchromesh mechanism, by sending to the traction machine, before the coupling of the pinion to the primary shaft, a torque command (T1 ref) which is dependent on a torque signal (T1 calc) calculated to minimize the discrepancy (σ) between the primary speed (ω1) and the secondary speed (ω2) multiplied by the reduction ratio (K) between these two shafts, characterized in that the calculated torque (T1 calc) is corrected by the acceleration of the secondary shaft (θ) in order to construct an intermediate signal (T*1) that takes account of the energy supplied by the traction machine in order to minimize the speed discrepancy (σ).