Actuators refine automatic manual transmission

Edited by the Engineeringtalk editorial team Apr 29, 2008

Two new actuator systems and a new industry standard control system are designed to make integration of the high-efficiency transmission as simple as possible.

Zeroshift, which launched the award-winning second generation of its revolutionary automatic gearbox technology last year, has moved into the next phase of development with two new actuator systems and a new industry standard control system aimed at making integration of the high-efficiency transmission as simple as possible.

The Zeroshift system replaces the synchromesh in a conventional manual gearbox with paired interlocking rings that allow ratios to be changed without torque interruption.

Shifts are made via an automated actuation system.

For the driver, it offers the refinement of a torque-convertor-based automatic and an expected improvement in economy of 2% compared with a manual gearbox, and 7% compared with a six-speed planetary automatic.

For the vehicle manufacturer, it offers CO2 reduction and a refined, low-cost automatic transmission based mainly on proven components from a conventional manual transmission.

For its early development work, Zeroshift used its own control systems.

But recognising the need for smooth integration by vehicle manufacturers, the company has now adopted a model-based control system using Matlab and Simulink for software development together with dSpace controller hardware.

All three industry standard products are already widely used throughout the automotive business and provide a fast track for vehicle manufacturers to integrate Zeroshift technology into their own vehicle transmissions.

"The benefits are enormous", says Senior Electronics Engineer, Steve Hands.

"We can now quickly offer solutions to customers using recognised tools which they are already familiar with".

The new system is fitted to Zeroshift development vehicles now and is undergoing testing.

Also under development are two new actuator systems that will also make the path to adopting Zeroshift technology much simpler.

Until this point, automatic operation of the selector mechanism has been achieved with pneumatic actuators and this will remain a natural choice for heavy duty vehicles already equipped with pneumatic systems.

But for cars, motorcycles and other applications, Zeroshift is now developing both an electric actuation system and a hydraulic system.

The electrical actuation system comprises a number of low-inertia, brushed motors to actuate the forks.

"The motors are equipped with the latest, iron-free magnets which deliver high performance and are more simple to control than brushless motors", explains Hands.

"The motors are off-the-shelf units with built-in gear heads and so provide a cost effective way of delivering quick, smooth shifting in a number of different transmission applications".

The hydraulic alternative provides a fast track for car manufacturers that are already using some kind of automated manual transmission (AMT).

"Most AMTs so far have relied on electrohydraulic actuation systems", says Hands.

"These actuators have hydraulic pistons controlled by hydraulic solenoid valves which provide proportional control of the pistons using pulsewidth modulation (PWM).

It's a system that will already be very familiar to most of the automotive industry and one which most car manufacturers are very comfortable with".

Work started on the hydraulic system at the end of 2007 and bench testing is nearly complete.

The next phase will be to test the system "live" in a rig before fitting transmissions equipped with it into development vehicles.

Apart from the fact that this offers an industry standard method of actuation", Hands continues.

"We will be able to change ratios at much higher engine speeds than before".

"We are also moving to smaller hydraulic pistons which deliver an even faster action, so Zeroshift will be suitable for even the highest performance applications".