Development Of EPS Induction Motor Control Based On Automatic Code Generation And Ethernet

The electric power steering(EPS)system is a kind of steering system depended on the motor to provide auxiliary assisted torque.Compared with the traditional mechanical and hydraulic power steering system,EPS has many advantages such as high fuel economy,good handling characteristics,good assembly,compact structure,light weight and so on.It has been taken by the major automobile companies and become the direction of the future car steering system.As a torque servo system,the EPS requires the power motor to have fast and accurate torque response and wide speed range.Induction motor can control the excitation current and torque current independently by the rotor field vector control method,and in this way the final effect can be comparable with the DC motor.How to determine the excitation current,that is,how to allocate the stator current into two parts of the excitation current component and the torque current component is the focus of this paper.After that,the induction motor can meet the EPS requirements under the premise of efficiency optimization.In this paper,further research is made on the excitation current decision and the field weakening control.Below the base velocity,the excitation current decision method proposed in this paper combines with the maximum torque per ampere strategy and the constant value strategy.When the excitation current is very small,using constant excitation current strategy can accelerate the response speed of the induction motor.When the excitation current is exceeded,the maximum torque current ratio strategy can reduce the energy loss of the induction motor.It is found in the research process that the rotor flux and the excitation current constitute a first-order inertia link.And because the maximum torque per ampere strategy adjusts the excitation current frequently,the flux response is too slow,and it further brings a slow torque response.In order to solve this problem,the excitation current differential method and the rotor flux differential method are proposed in this paper,and those two methods can accelerate the response speed of the rotor flux by constructing a new transfer function.Then,in order to further accelerate the torque response speed,the current adjustment algorithm of fuzzy PI,feedforward control and feedback decoupling is adopted.The voltage-loop flux weakening method based on current and voltage trajectory is proposed when the motor speed is greater than the base speed.Firstly,a voltage and current trajectory used in different work areas is planned in order to make the induction motor output as much torque as possible.Secondly,using the integral control weak-field algorithm designed in this paper,the excitation current and torque current are restricted to change according to the established trajectory.Finally,the two differential methods and the current adjustment algorithm proposed earlier are introduced into the voltage-loop flux weakening method.In order to monitor and debug the key variables in real time,the fast Ethernet technology is developed into the high frequency motor control program.And the use of the automatic code generation technology reduces the code-writing difficulty.By designed part of EPS motor controller PCBs and modified the induction motor test bed,the complete experimental environment has been successfully created.