Avshalom Suissa

Vehicle velocity estimation using nonlinear observers

Nonlinear observers for estimation of lateral and longitudinal velocity of automotive vehicles are proposed. The observers are based on a sensor suite that is standard in many new cars, consisting of acceleration and yaw rate measurements in addition to wheel speed and steering angle measurements. Two approaches are considered: first, a modular approach where the estimated longitudinal velocity is used as input to the observer for lateral velocity, and second, a combined approach where all states are estimated in the same observer. Both approaches use a tire-road friction model, which is assumed to be known. It is also assumed that the road is flat. Stability of the observers is proven in the form of input-to-state stability of the observer error dynamics, under a structural assumption on the friction model. The assumption on the friction model is discussed in detail, and the observers are validated on experimental data from cars.

Nonlinear vehicle side-slip estimation with friction adaptation

A nonlinear observer for estimation of the longitudinal velocity, lateral velocity, and yaw rate of a vehicle, designed for the purpose of vehicle side-slip estimation, is modified and extended in order to work for different road surface conditions. The observer relies on a road-tire friction model and is therefore sensitive to changes in the adhesion characteristics of the road surface. The friction model is parametrized with a single friction parameter, and an update law is designed. The adaptive observer is proven to be uniformly globally asymptotically stable and uniformly locally exponentially stable under a persistency-of-excitation condition and a set of technical assumptions, using results related to Matrosovs theorem. The observer is tested on recorded data from two test vehicles and shows good results on a range of road surfaces.

Vehicle sideslip estimation

The objective of this article is to develop a vehicle sideslip observer that takes the nonlinearities of the system into account, both in the theoretical analysis and the design. The design goals include reduction of the computational complexity compared to the EKF, to make the observer suitable for implementation in the embedded hardware, and a reduction in the number of tuning parameters compared to the EKF. Design is based on a standard sensor configuration, and is subjected to the extensive testing in the realist conditions.

Nonlinear Observer for Vehicle Velocity with Friction and Road Bank Angle Adaptation - Validation and Comparison with an Extended Kalman Filter

Many active safety systems in automotive vehicles, for instance yaw stability systems such as ESC/ESP, depend on information about vehicle velocity, in particular lateral velocity or side-slip angle, to be able to function properly. However, the vehicle velocity is rarely measured directly due to issues of cost and reliability, and must therefore in general be inferred from other measurements, such as wheel speed, steering angle, yaw rate, and acceleration measurements.

The Daimler-Benz steering assistant: a spin-off from autonomous driving

Based on the experience gained during 3000 km of autonomous driving on public highways, the Daimler-Benz steering assistant has been developed. As a link between purely manual and autonomous driving, this system supports the driver in keeping his lateral position on the lane while he remains in full control of the vehicle. It reduces the drivers steering task to global positioning, thus relieving him of the permanent fine tuning. To achieve this and compensate for environmental disturbances, the steering angle commanded by the driver is slightly modified by adding a correcting value via a small actuator. The hardware and software limit the controllers action to guarantee safety. Image processing is used to obtain the needed vehicle position and orientation on the road. System simulation on the Daimler-Benz driving simulator in Berlin reveal a considerable improvement of the vehicles straight-running properties, especially in curves. Test drivers accept this new system very well. Experiments on public roads with our test vehicle confirm these results.

Vehicle Velocity Estimation using Modular Nonlinear Observers

Nonlinear observers for estimation of lateral and longitudinal velocity of automotive vehicles are proposed, based on acceleration and yaw rate measurements in addition to wheel speed and steering angle. The observer for lateral velocity uses a tyre-road friction model. Exponential stability of the observers are shown. A structural assumption on the friction model is discussed. The observer structure is validated using experimental data from cars.

Estimation of road inclination and bank angle in automotive vehicles

We extend an observer design for estimation of the vehicle sideslip angle on horizontal surfaces to include estimation of the road inclination angle and the road bank angle. The design makes use of a nonlinear road-tire friction model, and the nonlinearity of the road-tire friction forces are taken into account in the theoretical analysis of the design. Using an absolute-stability argument we show that, under a set of technical assumptions, the origin of the observer error dynamics is globally exponentially stable. Taking unknown road-surface conditions into account, we discuss simultaneous estimation of the road bank angle and a road-tire friction parameter, which is complicated by the dependence of the friction-parameter estimation on lateral excitation of the vehicle. To improve performance on low-friction surfaces, we modulate the observer gains based on a set of practical conditions. Using experimental data from a passenger car, we investigate the performance of the approach.

Nonlinear Vehicle Velocity Observer with Road-Tire Friction Adaptation

A nonlinear observer for lateral velocity of an automotive vehicle is extended for robustness with respect to unknown road surface conditions. The observer uses a friction model parametrized with the maximum road-tire friction coefficient, and an adaptive parameter update law is designed for estimation of this coefficient. The adaptive nonlinear observer is proven to be uniformly globally asymptotically stable under a uniform 5-persistency-of-excitation condition, and a set of additional technical assumptions, using results related to Matrosovs theorem. The adaptive observer is validated using experimental data from a car

Nonlinear observer for vehicle velocity estimation

A nonlinear observer for estimation of lateral and longitudinal velocity of automotive vehicles is proposed, based on acceleration and yaw rate measurements in addition to wheel speed and steering angle measurements. Stability of the observer is proved in the form of input-to-state stability of the observer error dynamics, under an assumption on the friction model. This assumption is treated with some detail. The observers are validated on experimental data from cars.

Vertical Dynamics Emulation Using a Vehicle Equipped with Active Suspension

This paper presents an integrated active suspension controller for vertical dynamics emulation. The proposed controller consists of an active body controller and a force controller, that are both designed based on mathematical models derived from physical principles and also validated by experimental data. The efficacy of the proposed method is verified by not only realistic simulations in an advanced simulator but also by experiments on a test vehicle.