Integrated electric vehicle control by differential parameterization

The design of a tracking controller for electric cars in x-by-wire structure is presented to assign trajectories for the coordinates of the vehicle structure, which are shown to be a flat output. The model of the car is a detailed nonlinear two-track vehicle with all degrees of freedom in the three-dimensional space provided with redundant actuation. Each tire is equipped with two salient pole permanent magnet (PM-)synchronous machines for steering and driving. For the controller design, an overall model with a special differential-algebraic structure is derived. The tire forces and the torques of the electrical machines are used as fictitious inputs. With this particular modeling it is possible to decouple the dynamic part of the model in the given coordinates at the highest relative degree. To get a consistent behavior it is necessary to account for some algebraic constraints, in this case given by the tire model and the torque equations of the PM-synchronous machines. It is possible to parameterize all constraints and coordinates of the drive units by the coordinates of the vehicle structure and its derivatives. All these parameterizations can be derived analytically. With an additional tracking controller the approach is robust against parameter variations and pulse-shaped disturbances. The control of the electrical machines is integrated in the overall control law. By introducing additional coupling conditions it is possible to generate the desired torque for steering and driving by minimum current.