Mats Jonasson is a senior researcher in Vehicle Dynamics focusing on vehicle motion engineering and control in the field of electrification and automation of future vehicles.
This paper describes how differential braking can be used to turn a vehicle in the context of pro... more This paper describes how differential braking can be used to turn a vehicle in the context of providing fail-operational control for self-driving vehicles. Two vehicle models are developed with differential input. The models are used to explain the bounds of curvature that differential braking provides and they are then validated with measurements in a test vehicle. Particular focus is paid on wheel suspension effects that significantly influence the obtained curvature. The vehicle behavior and its limitations due to wheel suspension effects are, owing to the vehicle models, defined and explained. Finally, a model based controller is developed to control the vehicle curvature during a fault by differential braking. The controller is designed to compensate for wheel angle disturbance that is likely to occur during the control event.
There is provided a method for estimating friction between a tire of a vehicle and a road surface... more There is provided a method for estimating friction between a tire of a vehicle and a road surface, the method comprising acquiring, a front wheel axle torque, a rear wheel axle torque, a vehicle longitudinal acceleration, a vehicle pitch rate and wheel rotational velocities. The method further comprises determining a front wheel normal force and a rear wheel normal force, based on a center of gravity of the vehicle and the longitudinal acceleration; determining a longitudinal tire stiffness, jointly determining a vehicle longitudinal velocity, based on the wheel rotational velocities and vehicle longitudinal acceleration, and a vehicle pitch angle relative to the horizontal plane based on the vehicle pitch rate; and determining a friction coefficient between tires and ground based on the front and rear wheel axle torque, the front wheel normal force and the joint estimation of pitch angle and vehicle longitudinal velocity. There is also provided a system for performing the described method
2021 European Control Conference (ECC), Jun 29, 2021
This paper studies the optimization problem of autonomous bus parallel parking subjected to recta... more This paper studies the optimization problem of autonomous bus parallel parking subjected to rectangular geometry constraints. The parking space is a non-smooth and non-convex irregular polygon. We propose a novel method for modeling geometry constraints, which allows using the exact non-smooth parking space, while still being able to formulate the problem as a smooth nonlinear program. The focus of this paper is to compare our method to two other approaches of modeling rectangular geometry constraints, where one uses mixed-integers while the other approximates the rectangle as a smooth function. We show that our novel method prevents collisions and requires shorter computation time, where collision constraints are imposed on a limited number of points on the vehicle contour.
Demands for new functions and refined attributes in vehicle dynamics are leading to more complex ... more Demands for new functions and refined attributes in vehicle dynamics are leading to more complex and more expensive chassis design. To overcome this, there has been increasing interest in a novel chassis design that could be reused in the development process for new vehicle platforms and mainly allow functions to be regulated by software. The Autonomous Corner Module (ACM) was invented at Volvo Car Corporation (VCC) in 1998. The invention is based upon actively controlled functions and distributed actuation. The main idea is that the ACM should enable individual control of the functions of each wheel; propulsion/braking, alignment/steering and vertical wheel load. This is done by using hubmotors and by replacing the lower control arm of a suspension with two linear actuators, allowing them to control steering and camber simultaneously. Along with active spring/damper and wheel motors, these modules are able to individually control each wheel's steering, camber, suspension and spin velocity. This provides the opportunity to replace mechanical drive, braking, steering and suspension with distributed wheel functions which, in turn, enable new vehicle architecture and design. The aim of this paper is to present the vehicle dynamic potential of the ACM solution, by describing its possible uses and relating them to previous research findings. Associated work suggests chassis solutions where different fractions of the functions of the ACM capability have been used to achieve benefits in vehicle dynamics. For instance, ideas on how to use active camber control have been presented. Other studies have reported well-known advantages, such as, good transient yaw control from in-wheel motor propulsion and stable chassis behaviour from four-wheel steering, when affected by side wind. However, this technology also presents challenges. One example is how to control the relatively large unsprung mass that occurs due to the extra weight from the in-wheel motor. The negative influence from this source can be reduced by using active control of vertical forces. The implementation of ACM, or similar technologies, requires a well-structured hierarchy and control strategy. Associated work suggests methods for chassis control, where tyre forces can be individually distributed from a vehicle path description. The associated work predominately indicates that the ACM introduces new opportunities and shows itself to be a promising enabler for vehicle dynamic functions.
Methods and systems for generating and utilizing a road friction estimate (RFE) indicating the ex... more Methods and systems for generating and utilizing a road friction estimate (RFE) indicating the expected friction level between a road surface and the tires of a vehicle based on forward looking camera image signal processing. A forward-looking camera image is pre-processed, patch segmented (both laterally and longitudinally, as defined by wheel tracks or the like), transformed into a bird\u27s eye view (BEV) image using perspective transformation, patch quantized, and finally classified. The resulting RFE may be used to provide driver information, automatically control the associated vehicle\u27s motion, and/or inform a cloud-based alert service to enhance driver safety
Rolling Loss Optimisation of an Over-actuated Vehicle using Predictive Control of Steering and Ca... more Rolling Loss Optimisation of an Over-actuated Vehicle using Predictive Control of Steering and Camber Actuators
This paper describes how differential braking can be used to turn a vehicle in the context of pro... more This paper describes how differential braking can be used to turn a vehicle in the context of providing fail-operational control for self-driving vehicles. Two vehicle models are developed with differential input. The models are used to explain the bounds of curvature that differential braking provides and they are then validated with measurements in a test vehicle. Particular focus is paid on wheel suspension effects that significantly influence the obtained curvature. The vehicle behavior and its limitations due to wheel suspension effects are, owing to the vehicle models, defined and explained. Finally, a model based controller is developed to control the vehicle curvature during a fault by differential braking. The controller is designed to compensate for wheel angle disturbance that is likely to occur during the control event.
There is provided a method for estimating friction between a tire of a vehicle and a road surface... more There is provided a method for estimating friction between a tire of a vehicle and a road surface, the method comprising acquiring, a front wheel axle torque, a rear wheel axle torque, a vehicle longitudinal acceleration, a vehicle pitch rate and wheel rotational velocities. The method further comprises determining a front wheel normal force and a rear wheel normal force, based on a center of gravity of the vehicle and the longitudinal acceleration; determining a longitudinal tire stiffness, jointly determining a vehicle longitudinal velocity, based on the wheel rotational velocities and vehicle longitudinal acceleration, and a vehicle pitch angle relative to the horizontal plane based on the vehicle pitch rate; and determining a friction coefficient between tires and ground based on the front and rear wheel axle torque, the front wheel normal force and the joint estimation of pitch angle and vehicle longitudinal velocity. There is also provided a system for performing the described method
2021 European Control Conference (ECC), Jun 29, 2021
This paper studies the optimization problem of autonomous bus parallel parking subjected to recta... more This paper studies the optimization problem of autonomous bus parallel parking subjected to rectangular geometry constraints. The parking space is a non-smooth and non-convex irregular polygon. We propose a novel method for modeling geometry constraints, which allows using the exact non-smooth parking space, while still being able to formulate the problem as a smooth nonlinear program. The focus of this paper is to compare our method to two other approaches of modeling rectangular geometry constraints, where one uses mixed-integers while the other approximates the rectangle as a smooth function. We show that our novel method prevents collisions and requires shorter computation time, where collision constraints are imposed on a limited number of points on the vehicle contour.
Demands for new functions and refined attributes in vehicle dynamics are leading to more complex ... more Demands for new functions and refined attributes in vehicle dynamics are leading to more complex and more expensive chassis design. To overcome this, there has been increasing interest in a novel chassis design that could be reused in the development process for new vehicle platforms and mainly allow functions to be regulated by software. The Autonomous Corner Module (ACM) was invented at Volvo Car Corporation (VCC) in 1998. The invention is based upon actively controlled functions and distributed actuation. The main idea is that the ACM should enable individual control of the functions of each wheel; propulsion/braking, alignment/steering and vertical wheel load. This is done by using hubmotors and by replacing the lower control arm of a suspension with two linear actuators, allowing them to control steering and camber simultaneously. Along with active spring/damper and wheel motors, these modules are able to individually control each wheel's steering, camber, suspension and spin velocity. This provides the opportunity to replace mechanical drive, braking, steering and suspension with distributed wheel functions which, in turn, enable new vehicle architecture and design. The aim of this paper is to present the vehicle dynamic potential of the ACM solution, by describing its possible uses and relating them to previous research findings. Associated work suggests chassis solutions where different fractions of the functions of the ACM capability have been used to achieve benefits in vehicle dynamics. For instance, ideas on how to use active camber control have been presented. Other studies have reported well-known advantages, such as, good transient yaw control from in-wheel motor propulsion and stable chassis behaviour from four-wheel steering, when affected by side wind. However, this technology also presents challenges. One example is how to control the relatively large unsprung mass that occurs due to the extra weight from the in-wheel motor. The negative influence from this source can be reduced by using active control of vertical forces. The implementation of ACM, or similar technologies, requires a well-structured hierarchy and control strategy. Associated work suggests methods for chassis control, where tyre forces can be individually distributed from a vehicle path description. The associated work predominately indicates that the ACM introduces new opportunities and shows itself to be a promising enabler for vehicle dynamic functions.
Methods and systems for generating and utilizing a road friction estimate (RFE) indicating the ex... more Methods and systems for generating and utilizing a road friction estimate (RFE) indicating the expected friction level between a road surface and the tires of a vehicle based on forward looking camera image signal processing. A forward-looking camera image is pre-processed, patch segmented (both laterally and longitudinally, as defined by wheel tracks or the like), transformed into a bird\u27s eye view (BEV) image using perspective transformation, patch quantized, and finally classified. The resulting RFE may be used to provide driver information, automatically control the associated vehicle\u27s motion, and/or inform a cloud-based alert service to enhance driver safety
Rolling Loss Optimisation of an Over-actuated Vehicle using Predictive Control of Steering and Ca... more Rolling Loss Optimisation of an Over-actuated Vehicle using Predictive Control of Steering and Camber Actuators
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Papers by Mats Jonasson