A method for control of a rear-axle steering of a motor vehicle. A steering angle of wheels of a rear axle is set. Upon reaching a predetermined lateral acceleration of the motor vehicle, the steering angle and/or the gradient of the steering angle of the wheels of the rear axle is limited as a function of a coefficient of friction of a roadway surface on which the motor vehicle is moving.

An input torque fundamental component computation circuit includes: a torque command value computation circuit that computes a torque command value corresponding to a target value for steering torque that is to be input by a driver for drive torque obtained by adding the steering torque to an input torque fundamental component; and a torque F/B control circuit that computes the input torque fundamental component through execution of torque feedback control for causing the steering torque to follow the torque command value. A target steering angle computation circuit computes a target steering angle on the basis of the input torque fundamental component. A steering-side control circuit computes target reaction force torque on the basis of execution of angle feedback control for causing a steering angle to follow a target steering angle. The torque command value computation circuit computes the torque command value in consideration of the grip state amount.

Systems and methods are provided for generating adapted tuning parameters for target slip estimation, the parameters being adapted to real-time road surface conditions. The method includes, receiving, from a road surface detection module, a road surface condition, S.sub.n, from among N road surface conditions S, range of friction, mu, and a confidence level, Ci. The method receives sensor system data from a sensor system, and determines, as a function of S.sub.n, range of mu, and Ci, initial estimator values including an estimated initial frictional force {circumflex over ()}(0), an initial gain, P.sub.0, and an initial projected range of signal bounds, (P.sub.u) and (P.sub.l). The method tunes (i.e., adapts) the initial estimator values to generate therefrom adapted tuning parameters based on received inputs. The method outputs adapted tuning parameters.

A steering device includes an electric motor and an electronic control unit controls the electric motor. The electronic control unit includes a first friction torque computation circuit, a second friction torque computation circuit, a first load torque-column angle estimation circuit, a pinion angle estimation circuit, a second load torque estimation circuit, and an axial force estimation circuit. The first friction torque computation circuit computes first friction torque. The second friction torque computation circuit computes second friction torque. The first load torque-column angle estimation circuit estimates first load torque and a column angle. The pinion angle estimation circuit estimates an estimated pinion angle value. The second load torque estimation circuit estimates second load torque. The axial force estimation circuit estimates an axial force that acts on a rack shaft.

A method for terminating driving on the road shoulder by a transportation vehicle includes detection by a detection unit that the transportation vehicle is situated at least partially on a road shoulder, determination of a steering intensity of a manual steering maneuver, and assignment of one of at least two predetermined steering codes to the steering maneuver by a computing unit as a function of the steering intensity. An automatic intervention into a transportation vehicle control is carried out as a function of the assigned steering code.

A steer-by-wire power steering system including a lower-level mechanism that includes a servo motor and a steered wheel, and an upper-level mechanism that includes a steering wheel and an auxiliary motor, the lower-level mechanism being closed-loop controlled, at zero force, by a lower local loop including a feedback branch that measures or estimates an actual downstream force downstream of the servo motor and upstream of the point of contact between the wheel and the ground, so as to make the servo motor transparent, while the upper-level mechanism is closed-loop controlled, at zero torque, by an upper local loop including a feedback branch which measures or estimates an actual driver torque between the auxiliary motor and the steering wheel so as to make the auxiliary motor transparent, the lower and upper local loops being controlled by a single overall controller.

A method for friction coefficient determination on elastically connected subsystems, in which an overall system includes multiple subsystems and at least two subsystems are connected to one another by an elastic connection. The elastic connection has at least one static friction state and a sliding friction state for prescribed external state variables, in which the overall system is excited with a vibration having a variable excitation amplitude at a defined excitation frequency. The excitation amplitude is varied, in which a phase difference between the vibration and a measured reaction torque together with the excitation amplitude are recorded as a function of time, in which no phase difference occurs in the static friction state and a phase difference of 180 occurs in the sliding friction state. In a first step, the excitation amplitude is increased until a transition in the phase difference from 0 to 180 indicates the transition from the static friction state to the sliding friction state.

Provided is a steering system including a controller that controls an electric motor. The controller has a combined friction torque estimation unit that estimates a combined friction torque combining friction torques occurring in respective transmission devices including a first transmission device. The combined friction torque estimation unit has a slipping speed calculation part that calculates a slipping speed of the first transmission device based on an angular speed of the electric motor, a friction coefficient calculation part that calculates a friction coefficient of the first transmission device based on the slipping speed, a tooth flank normal force calculation part that calculates a normal force acting on a tooth flank of the first transmission device, and a friction torque calculation part that calculates the combined friction torque using the friction coefficient, the tooth flank normal force, and one or more preset correction factors.

A method and system for rack-and-pinion position adjustment for a steer-by-wire steering system for a motor vehicle. A module provides adjustment of the rack-and-pinion position, by determining a position error from a difference between desired and estimated value(s) of the rack-and-pinion position and the rack-and-pinion speed in a feedback structure, from which a control variable is determined for controlling the rack-and-pinion and a disturbance variable compensation for the control variable is carried out in a feedforward structure by means of a rack force estimation.

According to one or more embodiments, a method includes computing, by a steering system, a model rack force value based on a vehicle speed, steering angle, and a road-friction coefficient value. The method further includes determining, by the steering system, a difference between the model rack force value and a load rack force value. The method further includes updating, by the steering system, the road-friction coefficient value using the difference that is determined.