Fiche individuelle

Automotive industry is evolving towards more fault-tolerant actuators to fulfill future autonomous vehicles requirements. Critical applications such as steering or braking have to resist to fault occurrences while being low cost due to mass production market. Considering these two criteria, multiphase electric drives offer a good tradeoff between increasing the degrees of freedom and limiting system oversizing. This paper proposes to compare three multiphase electric drives for electro-hydraulic power steering for trucks: a five-phase machine and a six-phase machine both fed by a full bridge inverter (FBI), and a seven-phase machine fed by a standard half-bridge inverter (HBI). Several comparison criteria are considered in the meantime: motor, electronics, control and manufacturing parameters. Some of criteria are obtained from finite-element analysis (FEA), while others are derived from analytic formula or dynamic simulations. criteria are evaluated for each drive and then results are discussed In the given low-voltage high-current application, H-bridge inverter topology seems to be a promising solution. Both five-phase and six-phase present similar results. However, six-phase drive could be more interesting, as it could be brought close to standard three-phase solutions and adapted to dual-lane supply.

Automotive safety applications will be soon a standard based on market evolution trends. Actuators performing safety operations, such as steering or braking, need to be more reliable with a low manufacturing cost. Multiphase drives seem to be a good alternative to actuators redundancy, as it offers greater degrees of freedom with at a limited extra cost. These drives have been studied for a while, especially in other industries such as ship propulsion or aeronautic actuator. However, comparison between multiphase drives for a given application is rare. In this paper, a methodology is proposed to evaluate several drives for a safety automotive application. Some manufacturing assumptions have been made in order to narrow the study to five, six and seven phase permanent magnet synchronous motors (PMSM). Machines have been modeled using 2-D finite elements analysis (FEA) software in order to extract their parameters which will be used in dynamic simulations. Based on the obtained results, each drive is evaluated according to defined criteria and best solutions are highlighted. Considering a low voltage high current application, full bridge inverter topologies feeding a six-phase motor seem to be a promising solution.