On the enhancement of vehicle handling and energy efficiency of electric vehicles with multiple motors: the iCOMPOSE project

Electric vehicles with multiple motors allow torque-vectoring, i.e., the individual control of each powertrain torque. Torque-vectoring (TV) can provide: i) enhancement of vehicle safety and handling, via the generation of a direct yaw moment to shape the understeer characteristics and increase yaw and sideslip damping; and ii) energy consumption reductions, via appropriate torque allocation to each motor. The FP7 European project iCOMPOSE thoroughly addressed i) and ii). Theoretical analyses were carried out to design state-of-the art TV controllers, which were validated through: a) vehicle simulations; and b) extensive experimental tests, which were performed at rolling road facilities and proving grounds, using a Range Rover Evoque prototype equipped with four identical on-board electric powertrains. This paper provides an overview of the TV-related contributions of iCOMPOSE

Vehicle sideslip angle estimation using Kalman filters: modelling and validation

The knowledge of the vehicle sideslip angle provides useful information about the state of the vehicle and it is often considered to increase the performance of the car as well as to develop safety systems, especially in the vehicle equipped with Torque Vectoring control systems. This paper describes two methods, based on the use of Kalman filters, to estimate the vehicle sideslip angle and the tire forces of a vehicle starting from the longitudinal and yaw velocity data. In particular, these data refer to on-track testing of a Range Rover Evoque performing ramp steer maneuvers at constant speed. The results of the sideslip estimation method are compared with the actual vehicle sideslip measured by a Datron sensor and are also used to estimate the tire lateral forces

A Fast and Parametric Torque Distribution Strategy for Four-Wheel-Drive Energy-Efficient Electric Vehicles

Electric vehicles with four individually controlled drivetrains are over-actuated systems and therefore the total wheel torque and yaw moment demands can be realized through an infinite number of feasible wheel torque combinations. Hence, the energy-efficient torque distribution among the four drivetrains is crucial for reducing the drivetrain power losses and extending driving range. In this paper, the reference torque distribution is formulated as the solution of a parametric optimization problem, depending on vehicle speed. An analytical solution is provided for the case of equal drivetrains on the front and rear axles, under the experimentally confirmed hypothesis that the drivetrain power losses are monotonically increasing with the torque demand. The easily implementable and computationally fast wheel torque distribution algorithm is validated by simulations and experiments on an electric vehicle demonstrator, along driving cycles and cornering maneuvers. The results show considerable energy savings compared to alternative torque distribution strategies

Design, analysis and investigation of an independent suspension for passenger cars

The objective of this paper is the design of a front suspension. The layout used is the McPherson strut, widely adopted for road cars due to its simplicity and to the limited space required. The handling, comfort and durability of the suspension are strictly related to the position of the hardpoints, and to the elastic elements. A sensitivity analysis is carried out to investigate the roll behavior of a standard vehicle during cornering. A multi-body dynamics software is used to perform ramp-steer simulations on a full-vehicle model. Results show the different peculiarities of three specific cases of analysis, each of them emphasising the effects of a specific parameter on the whole system

Vehicle sideslip estimation for four-wheel-steering vehicles using a particle filter

The availability of the most relevant vehicle states is crucial for the development of advanced vehicle control systems and driver assistance systems. Specifically the vehicle sideslip angle plays a key role, yet this state is unpractical to measure and still not straightforward to estimate. This paper investigates a particle filter approach to estimate the chassis sideslip angle of road vehicles. The filter relies on a physical model of the vehicle and on measurements available from cheap and widespread sensors including inertial measurement unit and steering wheel angle sensor(s). The approach is validated using experimental data collected with the research platform RoboMobil (RoMo), a by-wire electric vehicle with wheel-individual traction and steering actuators. Results show that the performance of the proposed particle filter is satisfactory, and indicate directions for further improvement

On the dynamic analysis of a novel snake robot: preliminary results

In recent years, modular robotics has become of great interest in the robotics community. Among them, snake robots are among the most flexible and versatile type of mobile robots, well-suited to a large number of applications, such as exploration and inspection tasks, participation to search and rescue missions etc. The present paper investigates the design of a novel snake robot, named Rese_Q01, currently being designed at Politecnico di Torino. In order to characterise the dynamic behaviour of the robot, a simple vehicle dynamics model is developed and basic simulations are carried out for a first implementation of a unit consisting of two modules. Preliminary results show the influence of the robot velocity on the trajectory curvature radius, as well as the effect of different ground/tire friction conditions. This analysis is the first step in order to develop effective control strategies for robot trajectories

A real-time capable method for planning minimum energy trajectories for one degree-of-freedom mechatronic systems

The synthesis of optimal motion profiles has shown to be a successful and virtually inexpensive solution for enhancing energy efficiency of mechatronic systems. A typical application is the design of point-to-point motion profiles for one-degree-of-freedom mechatronic systems. This paper proposes a new method for designing minimum energy trajectories for servo-actuated systems. The problem is solved by exploiting the knowledge of the structure of the optimal solution. That allows to solve the motion design problem by solving a set of nonlinear equations and, if needed, some basic optimization procedures, formulated after some suitable continuity conditions. The herein proposed method applies to systems with and without energy regeneration capability, for maximum adaptability to most industrial applications. The method also handles jerk, acceleration, and velocity constraints, which are typical requirements in many practical applications. The number of equations and thereby the computational time depends on the number of active constraints and on whether negative power is dissipated or regenerated. Overall, the method results to be suitable for Real-Time applications, also in the most challenging case in which all the constraints are active and the system cannot regenerate negative electric power. The accuracy and the effectiveness of the planning method is tested numerically, by comparing the solution to the one obtained by a general purpose optimal control solver and then also experimentally using a lab prototype

The effect of the front-to-rear wheel torque distribution on vehicle handling: an experimental assessment

The front-to-rear wheel torque distribution influences vehicle handling and, ulti-mately, it affects key factors such as vehicle safety and performance. At a glance, due to part of the available tire-road friction being used for traction at the driven axle, a Front-Wheel-Drive (FWD) vehicle would be expected to be more understeering than a Rear-Wheel-Drive (RWD) vehicle. However, such effect may be counterbalanced, or even reversed, mainly due to the yaw moment caused by the lateral contribution of the traction forces at the front wheels. This paper proposes an experimental assessment, carried out on a fully electric vehicle with multiple mo-tors, allowing different front-to-rear wheel torque distributions. The results confirm that the yaw moment effect discussed is considerable, especially at low vehicle speeds and high steering an-gles. In particular, the RWD vehicle resulted more understeering than the FWD one at 30 km/h

On the Experimental Analysis of Integral Sliding Modes for Yaw Rate and Sideslip Control of an Electric Vehicle with Multiple Motors

With the advent of electric vehicles with multiple motors, the steady-state and transient cornering responses can be designed and implemented through the continuous torque control of the individual wheels, i.e., torque-vectoring or direct yaw moment control. The literature includes several papers on sliding mode control theory for torque-vectoring, but the experimental investigation is so far limited. More importantly, to the knowledge of the authors, the experimental comparison of direct yaw moment control based on sliding modes and typical controllers used for stability control in production vehicles is missing. This paper aims to reduce this gap by presenting and analyzing an integral sliding mode controller for concurrent yaw rate and sideslip control. A new driving mode, the Enhanced Sport mode, is proposed, inducing sustained high values of sideslip angle, which can be limited to a specified threshold. The system is experimentally assessed on a four-wheel-drive electric vehicle. The performance of the integral sliding mode controller is compared with that of a linear quadratic regulator during step steer tests. The results show that the integral sliding mode controller significantly enhances the tracking performance and yaw damping compared to the more conventional linear quadratic regulator based on an augmented singletrack vehicle model formulation. © 2018, The Korean Society of Automotive Engineers and Springer-Verlag GmbH Germany, part of Springer Natur

On the Energy Efficiency of Electric Vehicles with Multiple Motors

Electric Vehicles (EVs) with multiple motors permit to design the steady-state cornering response by imposing reference understeer characteristics according to expected vehicle handling quality targets. To this aim a direct yaw moment is generated by assigning different torque demands to the left and right vehicle sides. The reference understeer characteristic has an impact on the drivetrain input power as well. In parallel, a Control Allocation (CA) strategy can be employed to achieve an energy-efficient wheel torque distribution generating the reference yaw moment and wheel torque. To the knowledge of the authors, for the first time this paper experimentally compares and critically analyses the potential energy efficiency benefits achievable through the appropriate set-up of the reference understeer characteristics and wheel torque CA. Interestingly, the experiments on a four wheel-drive EV demonstrator show that higher energy savings can be obtained through the appropriate tuning of the reference cornering response rather than with an energy efficient CA