A new addition to the ABD range of K&C Machines, the SPMM 4000 HS meets an industry requirement to reduce the time from concept to manufacturing a new vehicle, with increased use of computer analysis and prediction techniques. It can measure suspension characteristics that are important to ride and handling in a wide range of vehicles from the smallest passenger cars to light trucks and MPVs.
Like the existing SPMM 4000 system, the new SPMM 4000 HS can be supplied as either a two or four wheel station machine. The four wheel station model will measure both axles of a vehicle simultaneously and provide a fast turnaround of just a few hours for producing a full suite of suspension and steering measurements for a vehicle. This has been further aided by the development of wheel centring compensation software which reduces vehicle set up time, as it is no longer necessary to manually centre the wheel plates when they are attached to the wheels.
In operation, the SPMM automatically subjects the suspension and steering of a vehicle to a variety of forces and displacements and measures the effects. Dynamic testing has been made possible by equipping the new system with high speed actuators capable of vertical excitation at frequencies of 5 Hz at speeds of 140 mm/s. It utilises ‘Dynamic wheel pad force control’ software which can accurately control wheelpad forces at frequencies of 5 Hz.
The SPMM 4000 HS records the wheel displacements and the forces and moments occurring at the tyre to road interface, caused by bounce, roll and pitch of the vehicle body and also by the application of simulated cornering, braking and traction forces. These include 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 4000 HS uses the new ABD Dynamic Arm wheel measurement system. Each arm has five high resolution rotary encoders and two high resolution linear encoders. The ABD Dynamic Arm has a dynamic measurement capability of 5 Hz, with measurement accuracies at 2 Hz of:
• 0.02 mm or better for displacements of up to ±10 mm and 0.05 mm or better for larger displacements up to ±75 mm
• 0.004° or better for steer, wheel spin and wheel camber displacements of up to ±1° and 0.01° or better for larger angles up to ±10°.
The measurement cross talks with the ABD Dynamic Arm are also considerably lower than for the corresponding draw wire encoder wheel position measurement system that is used on the existing SPMM 4000.
Using the new SPMM 4000 HS system, a large number of parameters may be measured including; suspension kinematic characteristics such as bump-steer and roll-steer, and suspension compliance characteristics such as suspension rates and roll stiffness. The kinematics and compliance characteristics of the steering system are also measured. Knowledge of these parameter values and characteristics is an essential aid to the thorough understanding of a vehicle’s performance in terms of steering, handling and ride.
