François Baudart

Torque Control Strategy of Polyphase Permanent-Magnet Synchronous Machines With Minimal Controller Reconfiguration Under Open-Circuit Fault of One Phase

This paper deals with the torque control of polyphase segment surface-mounted-permanent-magnet synchronous machines. First, we introduce a Lagrangian formulation for computing the optimal sinusoidal currents allowing to develop a given torque, both in normal operation mode and in fault operation mode (loss of one phase). Then, we present a torque control architecture allowing to switch from normal to fault operation mode with a minimum reconfiguration of the controller. All the theoretical results are validated by simulation and experiments on a test bench.

Original articles: Optimal current waveforms for torque control of permanent magnet synchronous machines with any number of phases in open circuit

Polyphase permanent magnet synchronous motors are well suited for electromechanical actuation systems demanding a high level of reliability. They are indeed able to run on a reduced number of phases and therefore to make the actuation system fault tolerant. The paper introduces a Lagrangian formulation for determining the optimal waveforms of the phase currents allowing the motor to develop the needed torque with one or more than one phase lost in open circuit. The method is then adapted to find sub-optimal sinusoidal currents in fault tolerant mode for machines with sinusoidal EMFs. Eventually the paper compares for this type of machine the oversizing imposed for maintaining the performance unchanged in fault tolerant operation mode, with or without imposing to the currents to remain sinusoidal.

Control strategy with minimal controller reconfiguration of fault tolerant polyphase PMSM drives under open circuit fault of one phase

Segment polyphase motors gain interest in applications requiring high performance and high reliability due to their high fault tolerance. This paper sums up the generalization of the vector control strategy of such motor and presents a method to adapt with a minimal reconfiguration the control strategy in the case of an open phase failure. Simulations results validate the method.

Control under normal and fault tolerant operation of multiphase SMPM synchronous machines with mechanically and magnetically decoupled phases

This paper deals with the control of multiphase surface mounted permanent magnet (SMPM) synchronous machines with mechanically and magnetically decoupled phases. As this type of machines is well suited for fault tolerant drives in critical applications as aerospace applications, the paper focuses on the power architecture and torque control strategies allowing to produce an almost ripple free torque both under normal and fault operation. The cases of a five-phase machine and of a six-phase machine are considered.

Optimal sinusoidal currents for avoiding torque pulsations after the loss of one phase in polyphase SMPM synchronous motor

Critical applications need actuators with high efficiency and high reliability. Electromechanical actuators can fulfill those criteria by using a polyphase PMSM with decoupled phases due to its high torque/mass ratio for the efficiency and its ability to perform its mission after the loss one phase for the reliability. This paper investigates how to avoid torque pulsations when one phase goes in open-circuit by adapting the currents in the remaining phases. It ends by a comparison of the solution imposing to the currents to remain sinusoidal with that imposing to the currents to minimize Joules losses.

Analysis of a new topology of flexible PCB winding for slotless BLDC machines

A significant improvement of slotless BLDC motor performance can be achieved by printing their windings on flexible printed circuit board (PCB). In comparison with windings made from copper wire, they may have more complex shapes in addition to a variable conductor cross-section along the winding loops. This paper presents a new winding topology taking the best of the capabilities offered by the flexible PCB technology and compare this to two existing topologies. It shows that a gain factor of about 10% on the motor performance can be reached with the new topology, confirming the high potential of the flexible PCB technology.

Original article: Analytical prediction of cogging torque in surface mounted permanent magnet motors

Cogging torque influences the control precision of permanent magnet motors used in actuation systems. This paper provides a rigorous analytical prediction method, easy to use in an optimization process. It relies on the fact that the magnetic energy variation due to one slot can be expressed by a coefficient k0 multiplying at the slot location the square of the airgap magnetic field generated by the magnets computed without taking the slotting effect into account.

Modelling and torque control of a five-phase permanent-magnet synchronous motor using tooth-concentrated winding technology

This paper deals with the modelling and the control of a five-phase machine using a tooth-concentrated winding technology. It is shown that the control of the torque can be easily performed in a generalized dq reference frame, and that with this control the motor can still operate when the feeding of one phase is lost. This makes the motor under study and its control architecture a good candidate when a fault-tolerant drive is needed.

Optimizing the control of permanent magnet polyphase segment synchronous motors in fault tolerant actuation systems

Polyphase permanent magnet synchronous motors are well suited for building high performance fault tolerant actuation systems. Such systems are found for instance in aerospace applications where reliability is a major concern. The first part of the paper summarizes the main features of polyphase permanent magnet segment synchronous motors. In the second part of the paper we study how to build a simple and efficient torque controller when the harmonic content of the machine EMFs can be neglected. In particular it is shown that this controller allows a very easy detection of a fault occurrence and a controller reconfiguration limited to an action on the link existing between the reference values of the phase currents and of the torque.

Comparison of FPCB windings of BLDC machines with paralelly and radially magnetized rotor poles

A technological leap is occurring in slotless brushless motors. Windings made of copper wires are replaced by windings printed on a flexible PCB. This technology offers a potential of new shapes and new topologies of the windings, increasing the efficiency of the slotless brushless motor. This paper is a contribution to this new field of research, investigating deeply curved loop windings, and comparing the shapes obtained in case of radially or parallely magnetized magnets, and AD or DC current feeding.