An efficiency optimization method of permanent magnet synchronous machine for electric vehicles applications is researched. Considering iron loss equivalent resistance and direct torque control scheme, the relationship of stator flux and power loss is derived based on loss model. And then the real-time optimal target flux can be obtained through the relationship of d-axis stator flux, target torque and electric speed at the minimum loss situation. A fitting curve of iron loss equivalent resistance versus speed is obtained by simulation. This makes the iron loss equivalent resistance closer to the actual value compared with the fixed value. Simulation results show that the motor efficiency has been improved compared with traditional direct torque control.
To achieve that the mobile warehouse robot follows the given desired path quickly and smoothly, the MPC and LQR steering control algorithms are applied based on the lateral kinematic constraints of the vehicle. First, the Ackermann kinematic modelling of the mobile platform is performed. The nonlinear model is linearized and discretized to create a discrete state space model of the mobile robot. Under the same conditions, a lateral control system based on MPC and LQR is designed for the mobile robot. A performance comparison of parameters such as different vehicle speeds, straightline trajectory tracking, curve trajectory tracking and algorithm consumption time is performed. The simulation shows that the LQR and MPC controllers can calculate the vehicle's steering angle in real time according to the road curvature and drive according to the preset desired path.
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