Predictive control of extended-range APU based on relaxed constrained Hammerstein nonlinear model

In view of the speed control of the working point switching process of the extended-range auxiliary power unit （APU），a predictive control strategy based on the Hammerstein nonlinear model was proposed.The excitation data were identified by sparse least squares support vector machine-adaptive chaotic particle swarm optimization （SLSSVM-ACPSO） algorithm，and the Hammerstein nonlinear model of engine was established.When solving the optimal control sequence in model predictive control，the relaxation factor was used to relax the constraint boundary，and the active set method （ASM）-ACPSO combination algorithm was used to obtain the solution.The variable predictive time domain strategy was applied in the control process.The system simulation model was established，and the simulation results showed that in the processes of switching from the warming-up point to low load point and from the low load point to the medium load point，the stabilization times were 2.57 s and 2.77 s respectively，and the speed overshoot rates were 2% and 1.6% respectively，which were better than the two comparison strategies.In the process of switching from medium load point to the high load point，the speed overshoot rate was relatively larger，but the change of torque was more smooth in the control process.The simulation result showed that the model predictive control strategy for APU system had fast speed response，small speed and torque overshoot rate，and exhibited good dynamic control effect.