Johannes Edrén

Utilisation of optimisation solutions to control active suspension for decreased braking distance

This work deals with how to utilise active suspension on individual vehicle wheels in order to improve the vehicle performance during straight-line braking. Through numerical optimisation, solutions have been found as regards how active suspension should be controlled and coordinated with friction brakes to shorten the braking distance. The results show that, for the studied vehicle, the braking distance can be shortened by more than 1 m when braking from 100 km/h. The applicability of these results is studied by investigating the approach for different vehicle speeds and actuator stroke limitations. It is shown that substantial improvements in the braking distance can also be found for lower velocities, and that the actuator strokes are an important parameter. To investigate the potential of implementing these findings in a real vehicle, a validated detailed vehicle model equipped with active struts is analysed. Simplified control laws, appropriate for on-board implementation and based on knowledge of the optimised solution, are proposed and evaluated. The results show that substantial improvements of the braking ability, and thus safety, can be made using this simplified approach. Particle model simulations have been made to explain the underlying physical mechanisms and limitations of the approach. These results provide valuable guidance on how active suspension can be used to achieve significant improvements in vehicle performance with reasonable complexity and energy consumption.

Implementation and evaluation of force allocation control of a down-scaled prototype vehicle with wheel corner modules

The implementation of wheel corner modules on vehicles creates new possibilities of controlling wheel forces through the utilisation of multiple actuators and wheel motors. Thereby new solutions fo ...

Scale model investigation of the snaking and folding stability of an articulated frame steer vehicle

This paper describes the development and evaluation of an articulated frame steer testvehicle on a model-scale. Vehicles with articulated steering are known to exhibit unstable behaviour in the for ...

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.