‘Smart fluid’ & technology enables motion control

Cary, N.C.—Pneumatic motion control has received a boost from a novel development by Lord Corp. which it calls Rheonetic technology. The design consists of braking devices, containing magnetorheological (MR) fluids, placed functionally in parallel with standard pneumatic actuators. Closed-loop feedback from a position sensor makes possible the accurate, robust motion control.

By Staff June 1, 1999

Cary, N.C.—Pneumatic motion control has received a boost from a novel development by Lord Corp. which it calls Rheonetic technology. The design consists of braking devices, containing magnetorheological (MR) fluids, placed functionally in parallel with standard pneumatic actuators. Closed-loop feedback from a position sensor makes possible the accurate, robust motion control. MR fluids have the ability to rapidly change consistency from fluid to near solid when exposed to a magnetic field. Variable force/control can be obtained by changing the fluid’s apparent viscosity under a varying magnetic field. Magnetorheological fluid technology answers limitations of compliance, complexity, and sensitivity to friction and air quality of standard pneumatic motion systems.

In one product version, linear controllable MR fluid brakes are clamped in parallel with an air cylinder. A controller commands a directional solenoid valve and the MR fluid brakes to allow tracking of complex position and velocity profiles, says Lord. Features of this light-duty actuator include strokes up to 24 in. and thrust range of 16-32 lb (at 20-40 psi operating pressure).

A second implementation couples a rotary MR fluid brake to the linear output of an air cylinder via a rack-and-pinion device. This higher capacity actuator offers strokes up to 16 in. and 85 lb maximum thrust (at 120 psi). For an 11-lb payload and 80 psi operation, typical positioning accuracy of 0.020 in. is available at 10 in./sec average speed. Accuracies increase with lower positioning speeds.

Lord Corp., Materials Div.