Driveline engineering specialist, Drive System Design (DSD), presented two technical papers at the 15th International CTI Symposium in Berlin (5-8 Dec) on Automotive Transmissions, HEV and EV Drives. The first, entitled ‘Highly integrated motor design for layshaft transmissions’, showed the benefits of integrating a bespoke electric motor within the transmission of a hybrid vehicle. The second, entitled ‘The future for connected drivetrain systems’ investigated the potential for powertrain design optimisation and cost reduction, as a result of increased vehicle connectivity.

Drive System Design (DSD) is an award winning engineering consultancy specialising in the engineering, development and control of transmission and future driveline systems.

“Designing the motor and transmission together enables a much higher level of system optimisation to be achieved,” explained DSD’s Technical Director, Alex Tylee-Birdsall. “Not only is the overall system lighter, more compact and more efficient; greater functionality can be provided, and costs saved through the elimination of certain components.”

The paper presents a new composite electrical machine design which packages inside a layshaft transmission as an additional parallel shaft. The advantages of the lightweight and low-inertia e-machine design were highlighted with respect to transmission weight, package and shift speed. The longer, smaller diameter rotor minimises the rotational inertia of the e-machine, improving the dynamic response whilst taking advantage of the length available in the base transmission package.

Unlike previous hybrid transmissions, designed in isolation and using a conventional motor type, the integration and optimisation of the two components together enables the e-machine to be used to perform multiple powertrain functions. The presentation covered such operations as layshaft synchronisation and electric creep, alongside the normal hybrid functions: regenerative braking and torque support.

By using the e-machine to displace existing components in the transmission such as shift elements, some of the additional cost and weight of a hybrid system can be offset by savings in the base gearbox. This entails designing the motor to meet the specific requirements of the transmission while, at the same time, adapting the transmission to better support the needs of the motor.

The paper includes examples of synergies such as active direct oil cooling of the e-machine windings to improve the power density while avoiding the need to package a water cooling jacket. The potential benefits of the system when used with 12V, 48V or high voltage vehicle electrical architectures was also outlined. The paper was presented on 6th December at 14:15 by Miriam Lorenzo, principal engineer, Control and Electronics.

The ability to continuously exchange data between the vehicle, the internet and a range of connected devices presents opportunities to save weight and cost by no longer designing for the 99th percentile driver, without impairing reliability.

“Weight and cost reductions of up to 20% are theoretically possible, by designing for the typical user instead of the most extreme,” comments DSD Director, David Kelly. “If accurate data can be collected, including short-duration torque ‘spikes’, a lighter, more representative duty cycle can be used during design and development. The risk of failures associated with the most aggressive drivers can be avoided by using information from real-time condition monitoring to schedule replacement or repair before such events occur.”

Throughout the symposium, DSD also exhibited its technology within the concurrent Transmission Expo. The company’s current focus is on robust, low noise gear design for volume production, efficiency improvement processes for existing and novel axles and transmissions, light-weighting, and eDrive solutions for EV/Hybrid architectures.