1,721,024 research outputs found
Vehicle Dynamics—Fundamentals
No full textThis Chapter presents the fundamental concepts of vehicle dynamics, in a rigorous yet relatively brief fashion. Bearing in mind the lack of unanimous conventions and stressing the need to fully control the hypotheses behind any model, formula or reasoning, this Chapter presents the three constituents of any (full) vehicle dynamics model: constitutive equations (tire model), congruence equations (kinematics), equilibrium equations (rigid body dynamics). Then, further insights and practical considerations are provided on a bunch of relevant aspects, including: radius of curvature (often misunderstood), sideslip angle (often not investigated with adequate depth), classical—and novel—perspectives on understeer and steady-state handling behavior
Design of a Rule-Based Energy Management System for a 3-Motor Vehicle with a Battery and a Fuel Cell: IEEE Motor Vehicle Challenge 2023
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Energy-optimal motion laws for servo-actuated systems considering asymmetric transmission efficiency
No full textThe synthesis of optimal motion trajectories is a well-established and cost-effective approach to improving the energy performance of mechatronic systems. This work introduces a method for the generation of energy-optimal trajectories in servo-actuated systems incorporating transmissions with non-unitary efficiency and with asymmetric (direct/reverse) power transmission behavior.The importance of incorporating the efficiency effect relies on the fact that the actual dynamics shows a not-smooth behavior, making the ideal system prediction erratic and the solution of the minimum-energy problem challenging. The proposed approach takes advantage of the known structure of the optimal solution, allowing the motion planning problem to be reformulated as an iterating quadratic programming problem. Optionally, a set of nonlinear equations has to be solved if acceleration/jerk limits are considered. These are constructed on the basis of continuity conditions that ensure physical and dynamical consistency. The formulation allows for real-time implementation, thus extending the applicability of minimum-energy trajectories in industrial scenarios, as general-purpose solvers do not cope with real-time requirements. Finally, the energy-saving capabilities are shown through comparison with a standard double-S law
Vehicle sideslip angle estimation for a heavy-duty vehicle via Extended Kalman Filter using a Rational tyre model
Full text linkVehicle sideslip angle is a key state for lateral vehicle dynamics, but measuring it is expensive and unpractical.
Still, knowledge of this state would be really valuable for vehicle safety systems aimed at enhancing vehicle safety, to help to
reduce worldwide fatal car accidents. This has motivated the research community to investigate techniques to estimate
vehicle sideslip angle, which is still a challenging problem. One of the major issues is the need for accurate tyre model
parameters, which are difficult to characterise and subject to change during vehicle operation. This paper proposes a new
method for estimating vehicle sideslip angle using an Extended Kalman Filter. The main novelties are: i) the tyre behaviour
is described using a Rational tyre model whose parameters are estimated and updated online to account for their variation due
to e.g. tyre wear and environmental conditions affecting the tyre behaviour; ii) the proposed technique is compared with two
other methods available in the literature by means of experimental tests on a heavy-duty vehicle. Results show that: i) the
proposed method effectively estimates vehicle sideslip angle with an error limited to 0.5 deg in standard driving conditions,
and less than 1 deg for a high-speed run; ii) the tyre parameters are successfully updated online, contributing to outclassing
estimation methods based on tyre models that are either excessively simple or with non-varying parameters
Robotic device for assisting human force
Full text linkA robotic device (100) for generating forces to assist or to resist the movement of the human body comprises a frame (110) that has a fixed point (A) and an articulation point (O) arranged at a predetermined mutual distance (a1), and a proximal arm (120), pivotally connected to the frame (110) at the articulation point (O). The proximal arm (120) has a loading point (O' ) arranged at a predetermined distance (L1) from the articulation point (O) along a proximal axis (125) having a predetermined direction (x). The proximal axis (125) is adapted to carry out a first rotation of a predetermined amplitude (θ1) in the plane (n) that contains the fixed point (A) and the proximal axis (125). The robotic device (100) also comprises an elongated resilient proximal element (160) that has a predetermined stiffness (k1) and that is constrained to proximal arm (120) and to the frame (110), in order to generate an interaction moment (Mini) with respect to the articulation point (O). The interaction moment (Min1) acts on the proximal arm (120) and is configured to generate an interaction force (Fin1) on the proximal arm (120) parallel to the direction (y) and applied to the loading point (Ο' ). The robotic device (100) also comprises a carriage (111) that is slidingly arranged on the proximal arm (120) and that has a first balancing point (B) arranged on the proximal axis (125) and arranged at a predetermined balancing distance (b1) from the articulation point (O). The carriage (111) is arranged to move along the proximal axis (125), in order to adjust the balancing distance (b1). An adjusting means is provided (112, 112', 113, 113', 114) arranged to actuate automatically the carriage (111) along the proximal axis (125)
On the vehicle sideslip angle estimation: a literature review of methods, models and innovations
Full text linkTypical active safety systems controlling the dynamics of passenger cars rely on real-time monitoring of the vehicle sideslip angle (VSA), together with other signals like wheel angular velocities, steering angle, lateral acceleration, and the rate of rotation about the vertical axis, known as the yaw rate.
The VSA (aka attitude or “drifting” angle) is defined as the angle between the vehicle longitudinal axis and the direction of travel, taking the centre of gravity as a reference. It is basically a measure of the misalignment between vehicle orientation and trajectory therefore it is a vital piece of information enabling directional stability assessment, in transients following emergency manoeuvres for instance. As explained in the introduction the VSA is not measured directly for impracticality and it is estimated on the basis of available measurements like wheel velocities, linear and angular accelerations etc.
This work is intended to provide a comprehensive literature review on the VSA estimation problem. Two main estimation methods have been categorised, i.e. Observer-based and Neural Network-based, focusing on the most effective and innovative approaches. As the first method normally relies on a vehicle model, a review of the vehicle models has been included. Advantages and limitations of each technique have been highlighted and discussed
New Gravity Balancing Technique and Hybrid Actuation for Spatial Serial Manipulators
No full textThe problem of gravity balancing of robotic systems has been investigated for a long time. A big amount of different designs has been developed so far, but with several limitations: applicability only to planar kinematics or some particular spatial ones, encumbrance and reduced workspace of the robot, complication of both theoretical and practical implementation. This chapter deepens a new simple technique for gravity balancing any spatial serial manipulator with rotational joints, using a number of springs less or equal to the number of degrees of freedom of the manipulator. Then, such technique is extended to a concept of actuation for robotic systems. Given a robotic manipulator and a force to exert at the level of the end effector, there is no energy consumption regardless of the configuration of the system (like in passive systems), as long as magnitude and orientation of the required force are fixed. Changes in magnitude and/or orientation of the exerted force require some energy to be achieved (like in active systems). Such combined features make an hybrid system with several benefits: low energy consumptions, simplified control and intrinsic safety of the system, with wide prospects in robotics
Vehicle Sideslip Angle estimation under critical road conditions via nonlinear Kalman filter-based state-dependent Interacting Multiple Model approach
Full text linkThe knowledge of Vehicle Sideslip Angle (VSA) can play an essential role in active safety vehicle control systems. However, due to the high costs of sensing instruments, this information is difficult to be directly measured onboard of series production vehicles, restricting de facto its application in practice. It follows that there is a need for online VSA estimation methods only based on available measurements from low-cost sensors. From this perspective, this work proposes a strategy based on Interacting Multiple Model (IMM) filters, which does not require tyre–road friction coefficient knowledge. By integrating the available onboard sensor data, the IMM estimates relevant information in different driving conditions leveraging a 2-Degrees Of Freedom (DOF) single-track vehicle model embedding a Dugoff tyre representation. Two alternative IMM algorithms based on the Extended (EKF) and Unscented Kalman filter (UKF) are developed. Moreover, while usually the transition probabilities among models in classical IMMs are fixed and set on prior information and/or dedicated analysis, here these conservative hypotheses are relaxed introducing a state-dependent Markov transition matrix based on a novel model switching algorithm. The effectiveness of the new proposed methods is evaluated on extensive non-trivial simulation scenarios through a Monte Carlo analysis exploiting an accurate 15-DOF vehicle model via a purposely designed high-fidelity co-simulation platform embedding the dSPACE software Automotive Simulation Model (ASM). Results provide a meaningful comparative performance analysis between the IMMEKF and IMMUKF solutions, as well as with respect to traditional IMM based on constant probabilities transition matrix, blue in both the EKF and UKF configuration. Finally, the developed IMM-based estimation strategy is tested in two realistic driving scenarios to assess the VSA estimation accuracy in case of abrupt changes in road surface conditions
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