Protective control system for magnetic suspension and magnetically suspended devices

In a magnetic suspension apparatus of the type in which a suspended member is in inherently unstable equilibrium along a major suspension axis thereof, said apparatus including spaced apart stop means for limiting the maximum displacement of said suspended member along said major axis, a servo loop for normally stabilizing said suspended member along said major axis including electromagnetic actuator means for normally positioning said suspended member apart from said stop means, said servo loop including integrator means responsive to energization of said electromagnetic actuator means for supplying a regenerative integral feed back signal to the input of said servo loop to compensate for any sustained force tending to maintain a corresponding sustained energization of said electromagnetic actuator means, the improvement providing means for conditioning said suspension apparatus for normal operation comprising:

• first means for supplying a signal varying in accordance with the position of said suspended member from said normal position along said major axis,
• said signal having a maximum value when said suspended member is at one of said stop means,
• second means responsive to said signal for normally controlling said electromagnetic actuator means to maintain said signal substantially at zero magnitude, thereby maintaining said suspended member in normal position, and
• switch means having a first state for initially removing said position signal from said electromagnetic actuator means and for supplying the same instead to said integrator means in a polarity opposite to said normal energization of said integrator means whereby to provide an integrator output to said loop in opposition to said position signal to reduce said maximum value thereof to a value insufficient to move said suspended member away from one of said stop means and having a second state for removing said position signal from said integrator means and for supplying said reduced value position signal to said electromagnetic actuator means.

In a magnetic suspension device of the kind in which first and second concentrically disposed components are cooperatively positioned by electromagnetic actuator means for relative rotation about an axis, said electromagnetic actuator means in normal operation supporting said first with respect to said second concentrically disposed component in unstable equilibrium at a predetermined locus substantially along said axis between stop means limiting abnormal relative excursion thereof, protective apparatus for said magnetic suspension device having first and second states and comprising:

• generator means for generating a first signal representative of the axial position of said first component with respect to said second component,
• integrator means,
• algebraic summation means responsive to said first signal and to said integrator means for producing a second signal for control purposes,
• said electromagnetic actuator means being responsive to said second signal,
• said integrator means being selectively responsive during said first state to an inverted version of said second signal and to current flow within said electromagnetic actuator means, and
• said integrator means being selectively responsive during said second state only to said electromagnetic actuator means current flow.