Basilio Lenzo

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

Electric vehicles (EVs) 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, an energy-efficient torque distribution among the four drivetrains is crucial for reducing the drivetrain power losses and extending driving range. In this paper, the optimal torque distribution is formulated as the solution of a parametric optimization problem, depending on the vehicle speed. An analytical solution is provided for the case of equal drivetrains, under the experimentally confirmed hypothesis that the drivetrain power losses are strictly monotonically increasing with the torque demand. The easily implementable and computationally fast wheel torque distribution algorithm is validated by simulations and experiments on an EV demonstrator, along driving cycles and cornering maneuvers. The results show considerable energy savings compared to alternative torque distribution strategies.

Torque Distribution Strategies for Energy-Efficient Electric Vehicles with Multiple Drivetrains

The paper discusses novel computationally efficient torque distribution strategies for electric vehicles with individually controlled drivetrains, aimed at minimizing the overall power losses while providing the required level of wheel torque and yaw moment. Analytical solutions of the torque control allocation problem are derived and effects of load transfers due to driving/braking and cornering are studied and discussed in detail. Influences of different drivetrain characteristics on the front and rear axles are described. The results of an analytically derived algorithm are contrasted with those from two other control allocation strategies, based on the offline numerical solution of more detailed formulations of the control allocation problem (i.e., a multiparametric nonlinear programming (mp-NLP) problem). The control allocation algorithms are experimentally validated with an electric vehicle with four identical drivetrains along multiple driving cycles and in steady-state cornering. The experiments show that the computationally efficient algorithms represent a very good compromise between low energy consumption and controller complexity.

New gravity balancing technique and hybrid actuation for spatial serial manipulators

The 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.

An Innovative Actuation Concept for a New Hybrid Robotic System

In this article a novel actuation concept of robotic manipulators is presented. The concept is based on an innovative extension of gravity balancing techniques using passive elements. It allows to exert, at the level of the end effector, a force of variable intensity and generic spatial orientation without any motor torque required during any movement of the manipulator, except when a change of the exerted force’s intensity and/or orientation is requested. So, a new hybrid machine can be realized combining the benefits of active and passive existing systems without their drawbacks, with possible very high potentials in robotics applications.

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.

Loading system mechanism for dielectric elastomer generators with equi-biaxial state of deformation

Dielectric Elastomer Generators (DEGs) are devices that employ a cyclically variable membrane capacitor to produce electricity from oscillating sources of mechanical energy. Capacitance variation is obtained thanks to the use of dielectric and conductive layers that can undergo different states of deformation including: uniform or non-uniform and uni- or multi-axial stretching. Among them, uniform equi-biaxial stretching is reputed as being the most effective state of deformation that maximizes the amount of energy that can be extracted in a cycle by a unit volume of Dielectric Elastomer (DE) material. This paper presents a DEG concept, with linear input motion and tunable impedance, that is based on a mechanical loading system for inducing uniform equi-biaxial states of deformation. The presented system employs two circular DE membrane capacitors that are arranged in an agonist-antagonist configuration. An analytical model of the overall system is developed and used to find the optimal design parameters that make it possible to tune the elastic response of the generator over the range of motion of interest. An apparatus is developed for the equi-biaxial testing of DE membranes and used for the experimental verification of the employed numerical models.