This paper details a unique method for estimating key vehicle states-body sideslip angle, tire sideslip angle, and vehicle attitude-using Global Positioning System (GPS) measurements in conjunction with other sensors. A method is presented for integrating Inertial Navigation System sensors with GPS measurements to provide higher update rate estimates of the vehicle states. The influence of road side-slope and vehicle roll on estimating vehicle sideslip is investigated. A method using one GPS antenna that estimates accelerometer errors occurring from vehicle roll and sensor drift is first developed. A second method is then presented utilizing a two-antenna GPS system to provide direct measurements of vehicle roll and heading, resulting in improved sideslip estimation. Additionally, it is shown that the tire sideslip estimates can be used to estimate the tire cornering stiffnesses. The experimental results for the GPS-based sideslip angle measurement and cornering stiffness estimates compare favorably to theoretical predictions, suggesting that this technique has merit for future implementation in vehicle safety systems

Integrating INS Sensors With GPS Measurements for Continuous Estimation of Vehicle Sideslip, Roll, and Tire Cornering Stiffness

While changing the handling characteristics of a conventional vehicle normally requires physical modification, a vehicle equipped with steer-by-wire can accomplish the same effect through active steering intervention. This paper presents an intuitive method for altering a vehicle's handling characteristics by augmenting the driver's steering command with full vehicle state feedback. The vehicle can be made more or less responsive depending on the driver's preference and particular operating conditions. Achieving a smooth, continuous change in handling quality requires both accurate state estimation and well-controlled steering inputs from the steer-by-wire system. Accurate estimates of vehicle states are available from a combination of global positioning system (GPS) and inertial navigation system (INS) sensor measurements. By canceling the effects of steering system dynamics and tire disturbance forces, the steer-by-wire system is able to track commanded steer angle with minimal error. Experimental results verify that with precise steering control and accurate state information, the handling modification is exactly equivalent to changing the front tire cornering stiffness.

/pdf/modification-of-vehicle-handling-characteristics-via-steer-2jgx5c4rvo.pdf

Modification of vehicle handling characteristics via steer-by-wire

Racecar drivers have the ability to operate a vehicle at its friction limit without losing control. If autonomous vehicles or driver assistance systems had similar capabilities, many fatal accidents could be avoided. To advance this goal, an autonomous racing controller is designed to gain insights into vehicle control at the friction limits. A bicycle model and a ‘ g-g ’ diagram are used to mimic racecar drivers’ internal vehicle model. Lanekeeping steering feedback and wheel slip feedback controllers are used to imitate drivers making steering and throttle corrections according to the vehicle responses. Experimental results on a low friction surface demonstrate that the controller can robustly track a path while operating at the limits of tyre adhesion and provide insights for the future development of vehicle safety systems.

/pdf/autonomous-vehicle-control-at-the-limits-of-handling-bfbbj266cq.pdf

Autonomous Vehicle Control at the Limits of Handling

Knowledge of the vehicle's lateral handling limits is important for vehicle control systems which aim to enhance vehicle handling and passenger safety. This paper presents a model-based estimation method that utilizes pneumatic trail information in steering torque to identify a vehicle's lateral handling limits, which are defined by the tire slip angle and peak lateral force limits. This method uses measurements available on many current production vehicles. Most importantly, it takes advantage of the early friction information encoded in the tire pneumatic trail. Pneumatic trail decreases as a function of the tire parameters even in the linear handling region, enabling early detection of the limits before they are reached. Experimental results on an independent front steering steer-by-wire research vehicle demonstrate the observer's ability to provide accurate real-time estimates of tire slip angle up to the limits of handling. Testing conditions include maneuvers performed on dry, flat paved road, as well as on lower-friction, dry gravel.

Estimation of Tire Slip Angle and Friction Limits Using Steering Torque

The term Intelligent Transport Systems (ITS) refers to any technology applied to transport and infrastructure to transfer information between systems, and to transport users, for improved safety, efficiency and environmental outcomes. This is a fast evolving field that includes stand-alone applications such as traffic management systems, information and warning systems installed in individual vehicles, as well as applications involving vehicle to infrastructure and vehicle to vehicle communications. Many ITS applications combine some or all of the above with Smartphone applications and GPS devices to enable transport users to make informed decisions.

Intelligent Transport Systems (ITS)

Starting with ABS (Antilock Brake System) the steps towards integrated active safety systems dealing with vehicle dynamics is shown. While ABS and TCS were initially designed as open loop controllers for the lateral vehicle motion a first approach towards closed loop control of the lateral vehicle motion for active safety systems was realized by ESP (Electronic Stability Program. Estimation algorithms and model following control are used with ESP to compensate for the lack of sensors. Since 2001 ESP is available for cars with an electro hydraulic brake system. The extension of ESP in combination with active front steering is expected to enter the market in 2003.

/pdf/evolution-of-electronic-control-systems-for-improving-the-59s91ewckc.pdf

Robert Bosch

Papers

Evolution of Electronic Control Systems for Improving the Vehicle Dynamic Behavior