Johan Andreasson

Global Chassis Control Based on Inverse Vehicle Dynamics Models

This work proposes to approach global chassis control (GCC) by means of model inversion-based feedforward with allocation directly on the actuator commands. The available degrees of freedom are used to execute the desired vehicle motion while minimizing the utilization of the tyre’s grip potential. This is done by sampled constrained least-squares optimization of the linearized problem. To compensate for model errors and external disturbances, high-gain feedback is applied by means of an inverse disturbance observer. The presented method is applied in a comparison of eight vehicles with different actuator configurations for steer, drive, brake and load distribution. The approach shows a transparent and effective method to deal with the complex issue of GCC in a unitized way. It gives both a base for controller design and a structured way to compare different configurations. In practice, the transparency supports automatic on-board reconfiguration in the case of actuator hardware failure.

Wheel force distribution for improved handling in a hybrid electric vehicle using nonlinear control

In this paper a vehicle motion controller is presented. The idea is to use generalized forces acting on the center of gravity of the vehicle and then use a control allocation-like method to distribute the generalized forces to wheel forces. The controller is designed based on feedback linearization of a simple vehicle model. The performance of the controller is evaluated by simulations on a more complex vehicle model. The proposed controller can handle the new flexibility introduced by new powertrain configurations, this is shown by using the same controller on two different vehicle configurations.

Global force potential of over-actuated vehicles

This paper formulates force constraints of over-actuated road vehicles. In particular, focus is put on different vehicle configurations provided with electrical drivelines. It is demonstrated that a number of vehicles possesses non-convex tyre and actuator constraints, which have an impact on the way in which the actuators are to be used. By mapping the actuator forces to a space on a global level, the potential of the vehicle motion is investigated for the vehicles studied. It is concluded that vehicles with individual drive, compared with individual brakes only, have a great potential to yaw motion even under strong lateral acceleration.

Utilization of Actuators to Improve Vehicle Stability at the Limit: From Hydraulic Brakes Toward Electric Propulsion

The capability of over-actuated vehicles to maintain stability during limit handling is studied in this paper. A number of important differently actuated vehicles, equipped with hydraulic brakes toward more advanced chassis solutions, are presented. A virtual evaluation environment has specifically been developed to cover the complex interaction between the driver and the vehicle under control. In order to fully exploit the different actuators setup, and the hard nonconvex constraints they possess, the principle of control allocation by nonlinear optimization is successfully employed. The final evaluation is made by exposing the driver and the over-actuated vehicles to a safety-critical double lane change. Thereby, the differently actuated vehicles are ranked by a quantitative indicator of stability.

Exploiting autonomous corner modules to resolve force constraints in the tyre contact patch

This paper presents a general force allocation strategy for over-actuated vehicles, utilising technologies where tyre forces can be more freely controlled than in conventional vehicles. For the purpose of illustration, this strategy has been applied and evaluated using a design proposal of an autonomous corner module (ACM) chassis during a transient open-loop response test. In this work, the vehicle has been forced to follow a trajectory, identical to the performance of a conventional front-steered vehicle during the manoeuvre studied. An optimisation process of tyre force allocation has been adopted along with tyre force constraints and cost functions to favour a desired solution. The vehicle response has been evaluated as open-loop, where tyre forces are shown to be allocated in a different manner than in conventional front-steered vehicles. A suggested approach for a control scheme of steering actuators is presented, where the actuator limitation is related to the lateral force possible. Finally, the force allocation strategy involves the ability to control vehicle slip independently from vehicle yaw rate. This opportunity has been adapted in the ACM vehicle in order to relax vehicle slip from the original trajectory description. In such circumstances, the ACMs demonstrate better utilisation of the adhesion potential.

Control Allocation based Electronic Stability Control System for a Conventional Road Vehicle

This paper shows how control allocation with an optimization formulation can be used as an on-line electronic stability control system for a conventional road vehicle. Control allocation is used in systems with more actuators than the degrees of freedom controlled, which are also known as over-actuated systems. Here it is assumed that the steering is solely managed by the driver. The control allocator uses the combustion engine and the four mechanical disc brakes to compensate any understeering or oversteering behaviour. Simulations showed that the suggested control system passed the proposed test procedure for Electronic Stability Control systems, sine with dwell, suggested by the National Highway Traffic Safety Administration (NHTSA).

Road friction effect on the optimal vehicle control strategy in two critical manoeuvres

This paper presents a research study on the optimal way to negotiate safety-critical vehicle manoeuvres depending on the available actuators and road friction level. The motive is to provide viable knowledge of the limitations of vehicle capability under the presence of environmental preview sensors. In this paper, an optimal path is found by optimising the sequence of actuator requests during the manoeuvres. Particular attention is paid to how the vehicle control strategy depends on friction. This study shows that the actuation of all the forces and torques on and around the vehicle centre of gravity is approximately scaled with friction, whereas at individual wheel level, the optimal force allocation will differ under different friction conditions. A lower friction level leads to lower velocities and load transfer, which influences the individual wheels’ tyre force constraints. However, the actuator response compared to the whole system is increased at a lower friction level.

Model-based design and control of long heavy vehicle combinations

Predicting and understanding the behavior of vehicle combinations is important both for the design of active and passive safety, as well as operability. This paper presents a modular structure to define articulated vehicle combinations that can handle arbitrary number of units and axles. It is illustrated how this modular approach can be used to design and control long heavy vehicle combinations.

Deployment of high-fidelity vehicle models for accurate real-time simulation

In the effort to shorten development cycles and with the reduced ability to test in real life, driver-in-theloop simulators are increasingly used by automotive OEMs and in Motorsports to enable engineers and drivers to experience a new vehicle design in a realistic environment before it is built. With the right level of accuracy, the same model can be applied in other real-time vehicle dynamics applications to allow for testing and verification in the development of new vehicle functions. This paper gives and overview of the requirements for automotive real-time application and the solution chosen. Emphasis is given on the model definition and real-time configuration as well as parameterization from existing data sources and integration of third party subsystem models.