E-Mobility Engineering 016 l Aurora Powertrains eSled dossier l In Conversation: Thomas de Lange l Automated manufacturing focus l Torque sensing insight l Battery Show Europe 2022 report l Sodium batteries insight l User interfaces focus

particularly in a highly transient system such as an electric traction drive system. The approach also reduces the need for design safety factors that consider manufacturing tolerance in production parts, measurement uncertainty for rotor temperature and other key variables, and the dependence on look-up tables for machine control. That would make it possible to tune the motor control on a ‘live’ basis for any operating condition and mode of the drive system. Dynamic torque feedback would also provide a dissimilar, comparative reference measurement to the motor phase currents, enabling new safety integrity functionality to be achieved. Although it is not a classical, dual modular redundant circuit – as in two identical sensing circuits – it provides an accurate and dissimilar comparison between the expected current at specific load points and the torque produced, which can deliver a higher level of safety integrity. If the measured current and actual torque produced differ, a fault would be raised and action taken. In effect, that would eliminate many of the issues around managing false-positive error reporting from current signals and signal processing in the control system. This proposed topology gives an additional degree of fault tolerance with the benefits of accurate torque feedback that provides the benefits of independently reporting motor load performance, as demonstrated above. Another advantageous technique that can be used is real-time harmonic analysis of the load. Depending on the bandwidth of the current transducer used, it is possible to detect motor and load harmonics, which could be used in predictive failure analysis. In addition to measuring shaft torque and temperature, it is possible to install additional SAW devices to measure temperature directly on the motor’s rotor. Placing a SAW device close to a magnet provides high-quality verification and continuous monitoring of rotor magnet temperature, which is very difficult to achieve even in a test lab environment with conventional measuring techniques. SAW devices have proven to be robust enough to be integrated into aerospace engines, as well as motorsport transmission systems with exceptional reliability. The relatively simple nature of the sensing element, combined with highly capable manufacturing process technology, means there are very few potential failure modes of the component, and those that do exist can be more easily controlled. Summary The main advantages of using direct torque measurement are intrinsically high-accuracy motor torque reporting, providing a redundant and dissimilar verification, and accurate characterisation of true load profiles where conventional inverter estimation inaccuracies detract from the true torque value. By using a low-cost shaft-type torque sensor, it is envisaged that there will be far less upfront machine characterisation needed during the initial set-up stage, giving major advantages in terms of a more accurate state of drive motor tuning and allowing for a faster time to market. the received back-scattered signal and calculates the value of the measurement. The antennas can also be configured to act as an inductive speed/position encoder, and the reader electronics can typically be integrated into the motor controller’s circuitry. The advantages of this approach are that measurement of micro-strain means no torsion bar is required, so a stiff system can be maintained. A torque measurement of ±1% can be achieved as well, meaning the torque signal can be brought into the control loop of the motor. It is also a completely wireless installation, so only small, light and passive components are required on the shaft. It is also immune to background interference and magnetic fields, measurement of torque and temperature is possible at more than 7 kHz, and its compact dimensions mean it can be easily packaged into a complex system. Embedding SAW sensors into an electric motor provides a new possibility for robust, high-speed torque and shaft temperature measurement that is suitable for use in production motor drive systems. These dynamic measurements can be used as a new control parameter to optimise the motor control to improve efficiency and safety integrity, The use of a radial coupler allows for a very compact installation. The coupler is a split-style stator, with the top half only shown here Winter 2022 | E-Mobility Engineering 47 Insight | Torque sensing