Synchronous Machine Starting Torque Control
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Solution Overview
Problem
Existing methods for controlling electric machines, such as permanent-magnet synchronous machines, face challenges in accurately estimating rotor position at standstill and low rotational speeds, leading to inadequate current and torque control, particularly in drive trains with direct engagement to wheels, resulting in torque surges and noise.
Innovation Solution
A method that involves predefining a default torque and adjusting the rotational speed by initially applying a higher torque to overcome drive train play and elasticity, then reducing it to the default torque to prevent mechanical vibrations, allowing for smooth and reliable starting of synchronous machines using digital sensor systems in hybrid and electric vehicles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a digital sensor system is used to determine rotor position, then measurement capability is provided, but at standstill and very low rotational speeds the rotor position cannot be adequately estimated due to the time interval between digital sensor signals
Solution Approach 1:
The patent applies preliminary action by defining a default torque M_V1 before starting the synchronous machine. This pre-defined torque value serves as a baseline that is adjusted during the starting process. By establishing this preliminary torque parameter, the system can properly control the machine during the critical low-speed phase where digital sensor signals are insufficient, thereby resolving the contradiction between measurement capability and low-speed operation.
2Speed
If higher torque is applied to overcome drive train play and elasticity, then the increase in rotational speed is greater, but mechanical vibrations are induced during the tensioning of the drive train
Solution Approach 1:
The patent applies dynamics by dynamically adjusting the torque from the pre-defined default value M_V1 during the starting process. The torque is modified based on the actual drive train tensioning state and rotational speed development. This dynamic adjustment allows the system to overcome drive train play and elasticity effectively while simultaneously preventing excessive mechanical vibrations, thus resolving the contradiction between speed increase and vibration generation.
Solution Approach 2:
The patent employs feedback mechanisms to monitor the drive train tensioning state and rotational speed, then uses this information to adjust the applied torque. By continuously feedbacking the actual system state and comparing it with the desired state, the control system can modulate the torque to achieve sufficient rotational speed increase while avoiding harmful mechanical vibrations during drive train tensioning.
3Power
If torque control is inadequate at low speeds, then current control and torque control are insufficient, but this leads to torque surges and noise generation in drive trains with direct wheel engagement
Solution Approach 1:
The patent applies preliminary action by pre-defining the default torque M_V1 before the starting process begins. This pre-established torque reference provides a foundation for subsequent torque control adjustments. By having this preliminary torque parameter in place, the system can maintain adequate torque control capability at low speeds, preventing torque surges and noise generation that would otherwise occur in drive trains with direct wheel engagement.
Solution Approach 2:
The patent applies parameter changes by modifying the torque parameter from the default value M_V1 during the starting process. The torque is adjusted as a function of rotational speed and drive train tensioning state, transforming the control parameter dynamically to maintain optimal torque control capability across the low-speed range, thereby preventing torque surges and noise while the machine accelerates from standstill.
Data Source
AI summary
In a method for starting a synchronous machine, a default torque is predefined, and a rotational speed of the synchronous machine is adjusted after starting. A torque which is higher than the default torque is predefined, and the higher torque is reduced in the subsequent second step to a positive value which is less than the default torque, and is increased to the default torque in a third step.