8.2.5. Interference-force estimation

An acceleration or deceleration force has to be calculated so that the prioritized longitudinal acceleration can be implemented using the actuators. Example: when the car is driving up hill the propulsive forces needed in order to achieve a given longitudinal acceleration are higher than when the car is travelling on a flat surface. Deceleration as the car ascends a gradient, on the other hand, requires less braking force than is the case on the flat. If these forces are to be computed correctly, exact values are required not only for the gradient, but also for the mass of the vehicle, rolling resistance, drag and other accelerating forces. There is no adequate system of sensors for all these interfering forces, so an estimated value is derived from a comparison of the following two variables:

• actual motion variables of the vehicle
• expected motion variables of the vehicle, forecast on the basis of the driving and braking forces currently applied.

The magnitude of the interference force estimated in this way is taken into account by addition or subtraction in the subsequent processing of the longitudinal-acceleration set-point.