Hysteretic equalization in redundant electrically operated fluid powered servopositioning apparatus

Claim 2

In redundant electrically operated fluid powered servopositioning apparatus having at least two channels each including a servovalve, signal summing means to which a command input signal is fed, an actuator operatively associated with the output of said servovalve and arranged to drive a common load member and feedback means arranged to provide a load position feedback signal to said signal summing means, the output of said summing means being fed to said servovalve, the improvement which comprises means for equalizing the outputs of said servovalves including, for each channel, equalizer means having a hysteresis characteristic for generating and feeding back to said signal summing means of a given channel an equalization signal responsive to the output of said servovalve of such given channel.

Claim 3

Apparatus according to claim 1 wherein said output of said servovalve is a differential pressure.

Claim 4

Apparatus according to claim 2 wherein said equalizer means comprises a piston, means for applying said differential pressure to said piston, means for preloading said Piston against movement induced by said differential pressure and for resisting increasingly but yielding such movement above such preloading effect, means including a movable member for generating an output electrical signal in response to movement of said member, friction means resisting yieldingly movement of said member, and lost motion drive means operatively interposed between said piston and member, said output electrical signal being said equalization signal.

Claim 5

Apparatus according to claim 2 wherein said equalizer means comprises a pair of pistons, means for applying said differential pressure to each of said pistons, common spring means operatively interposed between said pistons, means including a movable member for generating an output electrical signal in response to movement of said member, friction means resisting yieldingly movement of said member, and lost motion drive means operatively interposed between said pistons and member, said output electrical signal being said equalization signal.

Claim 6

Apparatus according to claim 2 wherein said equalizer means comprises a pair of pistons, common spring means operatively interposed between said pistons to bias them severally in opposite directions, means limiting movement of said pistons in said opposite directions, means for applying said differential pressure to each of said pistons to urge one to move in one of said directions and the other to move in the other of said directions, means including a movable member for generating an output electrical signal in response to movement of said member, friction means resisting yieldingly movement of said member, and lost motion drive means operatively interposed between said pistons and member, said output electrical signal being said equalization signal.

Claim 7

Apparatus according to claim 2 wherein said equalizer means comprises a body having piston stop surfaces defining partly a compartment, a pair of pistons severally slidably arranged in said compartment, common spring means constantly urging said pistons severally toward said stop surfaces, means for applying said differential pressure of said servovalve to each of said pistons so as to urge one to move toward its stop surface and the other to move away from its stop surface, linear variable differential transformer means including a probe, friction means resisting yieldingly movement of said probe, and lost motion drive means operatively interposed between said pistons and probe, the output electrical signal of said linear variable differential transformer means being said equalization signal.

Claim 8

Apparatus according to claim 6 wherein one of said pistons has oppositely facing first and second surfaces, the other of said pistons has oppositely facing third and fourth surfaces, and said lost motion drive means comprises passage means in said one of said pistons connecting said first and second surfaces, passage means in said other of said pistons connecting said third and fourth surfaces, a rod connected to said probe and extending through said passage means, a first lug fast to said rod opposite and adapted to engage said first surface, a second lug fast to said rod intermediate and adapted to engage either of said second and third surfaces and a third lug fast to said rod opposite and adapted to engage said fourth surface, the spacing between said lugs being such that said second lug is spaced substantially equally from said second and third surfaces when said first surface engages said first lug and said fourth surface engages said third lug.

Claim 9

Apparatus according to claim 6 wherein said friction means comprises a packing surrounding and wipingly engaging said probe.

Claim 10

Apparatus according to claim 7 wherein said friction means comprises a packing surrounding and wipingly engaging said rod.

Claim 11

Apparatus according to claim 2 wherein said equalizer means comprises pressure transducer means for providing a first output electrical signal related to said differential pressure, and electrical circuit means receiving said first output electrical signal as input and providing a second output electrical signal having a hysteresis characteristic, said second output electrical signal being said equalization signal.

Claim 12

Apparatus according to claim 10 wherein said electrical circuit means includes hysteresis circuit means and threshold circuit means.

Claim 13

Apparatus according to claim 11 wherein said hysteresis circuit means includes amplifier means, integrator means and biased diode means, and said threshold circuit means includes amplifier means and biased diode means.