SSTM From Anthony Best Dynamics OUTLINE SPECIFICATION SSTM 6102 issue 2



Steering System Test SSTM

SSTM From Anthony Best Dynamics OUTLINE SPECIFICATION SSTM 6102 issue 2


The Steering System Test Machine (SSTM) is a computer-controlled machine for applying force and displacement inputs to a vehicle’s steering system in the laboratory.



The SSTM is used to characterise steering system performance both objectively, using quasi-static and dynamic tests, and subjectively. Hardware in the Loop (HiL) testing can also be performed.

The frame of the machine allows the vehicle’s steering column and steering wheel to be mounted so that manual inputs can be applied to the system (a seat is provided for the driver), and steering feedback to be measured. Optionally, the machine can be interfaced with ABD’s SR30, SR60 or SR80 Steering Robots, to provide controlled position or torque inputs to the steering column.

The SSTM can also be supplied with an optional Hydraulic Power Pack to drive a proprietary vehicle power steering pump under speed control.



Rig Overview

Each rack actuator consists of an assembly of two individual torque motors (Mounted to a common shaft) which are driven together to achieve maximum load output, and which can be driven one at a time for tests that require lower force output with a better force resolution.
The lateral spacing of the rack actuators can be adjusted to suit different racks.

The control and integrated software suite

The control and integrated software suiteThe machine is driven by direct-drive servo motors. These are controlled using a programmable multi-axis controller, which ensures smooth synchronised motion of the axes.

The controller is interfaced to a computer, which controls the overall operation of the machine and provides the user interface.

The system is designed to be highly flexible and user-friendly with help screens and pop-up selection tables to allow new test sequences to be specified quickly and easily.



The measurement system

Angular position of the rack actuators and Steering robot, if fitted, is provided by high-resolution optical encoders. Force and torque feedback is from high resolution piezoelectric load cells that are built into each of the track rods, and steering robot torque reaction mechanism, if fitted. The analogue signals from the load cell amplifiers are captured by 16-bit A/D converters (ADCs) that are integral to the servo-controller. The load channel charge amplifiers also have switchable gains to allow very high resolution for tests where small forces are applied.

Additional analogue input channels can be added to the rig’s controller as an option, so that parameters external to the rig’s control systems can also be recorded (up to 12 16-bit ADC channels and sixteen 12-bit ADC channels are possible); contact ABD for the viability of other ADC configurations.


The rig can impart a wide variety of forces and displacements to a steering rack.

Any of the 4 possible axes (2 x rack actuators, Steering Robot, power steering pump motor) can be controlled simultaneously in any combination of the available control modes; with the one obvious exception that only one axis at a time can be in position control.

The rig can operate in standalone mode or in Hardware in the Loop (HiL) mode.

Command signals can be generated in a number of ways:


Command signal Description
Standard Template User definable Fishhook, square wave, trapezoidal wave, pulse wave, continuous sine, linear sine sweep and constant velocity sine sweep profiles
ASCII file Allows measured vehicle data to be used as command signals
User defined force/torque function of rack/steering wheel position i.e. Steering feel test – rack forces are generated as a function of rack position (linear, quadratic and cubic terms allowed)
ADC External analogue commands allow HiL tests


Typical tests are:


Test Description Details
Open loop force control frequency sweep Transfer function automatically displayed as Bode plot
Compliance tests Used to determine compliance in steering system
Friction tests Used to determine Rack, Column, and Ball-joint friction levels
Steering catch up Used to evaluate power assistance characteristics
Steering feel Rack forces generated as user defined function of rack displacement
Nibble Tests that generally use recorded vehicle data as command signals
On centre
Parking effort
Standard vehicle test manoeuvres (e.g. constant radius steady state, lane change etc)



A flexible graph-plotting facility is provided to allow any parameter to be plotted against any other.




Rig Dimensions & Weights
Overall length 2796 mm*
Overall width 2213 mm*
Overall Height 1781 mm*
Table surface height 800 mm (excluding grout thickness)
Overall weight 3.5 ton
Maximum vertical ground loading - 0.03 N/mm2
* Excluding control cabinet, optional hydraulic power pack & walkways
Applied Loads
Rack Actuator
Peak actuator torque (1 motor per actuator) 550 Nm (4.4kN for 0.125m lever arm)
Peak actuator torque (2 motors per actuator) 1100 Nm (8.8kN for 0.125m lever arm)
Maximum duration for peak torque (either 1 or2 motors per actuator) 30 s
Maximum continuous torque (2 motors per actuator) 400 Nm (3.2 kN for a 0.125m lever arm)
Maximum continuous torque (1 motor per actuator) 250 Nm (2.0 kN for a 0.125m lever arm)
Force Control
Force control Bandwidth (-3dB)   400 Nm (3.2 kN for a 0.125m lever arm)
Actuator asymmetry: Magnitude ±3%
  Phase ±2º
  Phase lag 5ms
Displacement Control
Displacement Control Bandwidth (-3dB) A 3 Hz
Steering Robot (SR30)
Maximum Continuous Steer Torque 30 Nm
Constant Velocities
Peak rack actuator velocity (no load) 5 rad/s
Peak steer robot velocity (no load) 40 rad/s

With the objective of continuous development and improvement, ABD reserve the right to change this specification without notice.



Company Information


AB Dynamics MF Japan

Grandbell bldg. 6F-F, 252 Naka-ku, Yokohama 213-0023 Japan
TEL : +81 (0)45 663 2869
FAX : +81 (0)45 663 2879
E-E-mail :

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