Heason delivers compact, zero-backlash, precision actuator

Anthony Best Dynamics supplies advanced testing systems to the global motor industry for research and development and for production quality control. The company designs and manufactures specialised systems for kinematics and compliance testing, vehicle dynamics testing on the track and steering system testing.

The moving body Suspension Parameter Measurement Machine (SPMM) is a proven system for use in kinematics and compliance testing. ABD's kinematics and compliance measurement machines measure the quasi-static suspension characteristics that are important to ride and handling. The machines measure the kinematic characteristics due to suspension and steering system geometries, and compliances due to suspension springs, anti-roll bars, elastomeric bushes and component deformations.

The SPMM uses precision electric actuators that avoid all the problems traditionally associated with hydraulic test equipment. The first SPMM manufactured by AB Dynamics was installed in 1997 and is still testing vehicles on a daily basis without requiring any major maintenance.

A large number of parameters may be evaluated, the principal ones being suspension rates and hysteresis, bump-steer, roll-steer, roll stiffness distribution, longitudinal and lateral compliance steer, and steering system characteristics. Knowledge of these parameter values and characteristics is an essential aid to the thorough understanding of a vehicles performance in terms of ride, steering and handling.

Test system architecture

The test system comprises a rigid table upon which the vehicle is mounted. The centre table can be moved with six degrees of freedom for kinematics measurements. Individual wheel stations have three degrees of freedom (X, Y, Delta) and integral six axis load platform. Wheel positions are measured using an accurate and easy to use optical encoder system. The optional MIMS (Moment of Inertia Measurement System) enables the SPMM to quickly measure vehicle centre of gravity, and inertias.

Heason's challenge was to develop a compact, zero-backlash, precision gear actuator that would allow ABD to offer higher rotation speeds while providing exceptionally smooth motion. Coupled with this, Heason's design brief was to package the new actuator to fit within an existing casting of the machine. Working closely with engineering expertise from Spinea SA (who Heason exclusively represent in the UK), Heason's mechanical design team developed a compact, zero-backlash gear actuator based around a custom Spinea TwinSpin bearing reducer with an Emoteq integrated frameless, brushless servo motor and high-resolution feedback device.

The new package not only achieved the higher rotation speed, but also surpassed the previous zero-backlash gear system in terms of smoothness, all in a more compact package. Actuator performance is impressive: 495Nm continuous torque, 1237Nm repeatable torque, 1000Nm/arcmin tilting stiffness, 110Nm/arcmin torsional stiffness,