Automatic load control system for hydraulic rotary power absorbers

Claim 2

In a load control system for controlling the retarding force characteristics of a hydraulic rotary power absorber in which the absorbed torque varies in proportion to the level of fill of the working fluid, the combination which comprises: speed signal generating means for generating a signal representative of the Rotational speed of the power absorber; torque signal generating means for generating a signal representative of the torque absorbed by the power absorber; and flow control means connected to the power absorber and adapted to be connected to a source of working fluid and responsive to said speed and torque signals for controlling the level of working fluid within the absorber to vary the absorbed torque in a predetermined manner in accordance with the speed and torque of the absorber.

Claim 3

The combination as defined in claim 1 wherein the flow control means is responsive to the speed signal squared and the torque signal to provide an absorbed torque which varies substantially with the square of speed changes.

Claim 4

In a load control system for controlling the retarding force characteristics of a hydraulic rotary power absorber in which the absorbed torque varies in proportion to the level of fill of the working fluid, the combination which comprises: speed signal generating means for generating a signal representative of the rotational speed of the power absorber; torque signal generating means for generating a signal representative of the torque absorbed by the power absorber; and flow control means connected to the power absorber and adapted to be connected to a source of working fluid and responsive to at least one of said speed and torque signals for controlling the level of working fluid within the absorber and the rate of flow of working fluid into or out of the absorber in accordance with the magnitude of the difference between the actual and desired values of speed and/or torque of the absorber.

Claim 5

In a load control system for controlling the retarding force characteristics of a hydraulic rotary power absorber in which the absorbed torque varies in proportion to the level of fill of the working fluid, the combination which comprises: speed signal generating means for generating a signal representative of the rotational speed of the power absorber; torque signal generating means for generating a signal representative of the torque absorbed by the power absorber; and flow control means connected to the power absorber and adapted to be connected to a source of working fluid and responsive to at least one of said speed and torque signals for controlling the level of working fluid within the absorber and the rate of flow of working fluid into or out of the absorber in accordance with the magnitude of the difference between the actual and desired values of speed and/or torque of the absorber.

Claim 6

The combination as defined in claim 3 wherein the flow control means includes electrically operated load and unload valves for controlling the fill and withdrawal of working fluid from the absorber and wherein the load and unload valves are arranged to open and close completely and the flow control means controls the duty cycle of the load and unload valves to provide a lower duty cycle as the value of the speed and/or torque approaches the desired value.

Claim 7

The combination as defined in claim 3 wherein the flow control means is responsive to the difference between the torque signal and the square of the speed signal to cause the absorbed power to follow a cubed function.

Claim 8

The combination as defined in claim 3 wherein the flow control means is responsive to the difference between the speed signal and a selected reference signal to cause the absorber to operate at a substantially constant speed.

Claim 9

The combination as defined in claim 3 wherein the flow control means is responsive to the difference between the torque signal and a selected reference signal to cause the absorber to operate at a substantially constant torque.

Claim 10

In a load control system for controlling the retarding force characteristics of a hydraulic rotary power absorber in which the absorbed torque varies in proportion to the level of fill of the working fluid, the combination which comprises: speed signal generating means for generating a signal representative of the rotational speed of the power absorber; torque signal generating means for generating a signal representative of the torque absorbed by the power absorber; and flow control means including at least one electrically operated load valve connected between the absorber and a source of working fluid for controlling the fill of the absorber and one electrically operated unload valve connected to the absorber for controlling the withdrawal of fluid from the absorber, the flow control means being responsive to the torque signal and the square of the speed for controlling the level of working fluid within the absorber to cause the absorbed torque to follow a cubed function.

Claim 11

In a load control system for controlling the retarding force characteristics of a hydraulic rotary power absorber in which the absorbed torque varies in proportion to the level of fill of the working fluid, the combination which comprises: speed signal generating means for generating a signal representative of the rotational speed of the power absorber; torque signal generating means for generating a signal representative of the torque absorbed by the power absorber; and flow control means including at least one electrically operated load valve connected between the absorber and a source of working fluid for controlling the fill of the absorber and one electrically operated unload valve connected to the absorber for controlling the withdrawal of fluid from the absorber, the flow control means being responsive to the torque signal and the square of the speed for controlling the level of working fluid within the absorber to cause the absorbed torque to follow a cubed function.

Claim 12

In a load control system for controlling the retarding force characteristics of a hydraulic rotary power absorber in which the absorbed torque varies in proportion to the level of fill of the working fluid, the combinatIon which comprises: speed signal generating means for generating a signal representative of the rotational speed of the power absorber; means for generating a selected reference signal; and flow control means including at least one electrically operated load valve connected between the absorber and a source of working fluid for controlling the fill of the absorber and one electrically operated unload valve connected to the absorber for controlling the withdrawal of fluid from the absorber, the flow control means being responsive to the difference between the speed signal and the reference signal to cause the absorber to operate at a substantially constant speed.

Claim 13

In a load control system for controlling the retarding force characteristics of a hydraulic rotary power absorber in which the absorbed torque varies in proportion to the level of fill of the working fluid, the combinatIon which comprises: speed signal generating means for generating a signal representative of the rotational speed of the power absorber; means for generating a selected reference signal; and flow control means including at least one electrically operated load valve connected between the absorber and a source of working fluid for controlling the fill of the absorber and one electrically operated unload valve connected to the absorber for controlling the withdrawal of fluid from the absorber, the flow control means being responsive to the difference between the speed signal and the reference signal to cause the absorber to operate at a substantially constant speed.

Claim 14

In a load control system for controlling the retarding force characteristics of a hydraulic rotary power absorber in which the absorbed torque varies in proportion to the level of fill of the working fluid, the combination which comprises: torque signal generating means for generating a signal representative of the torque absorbed by the power absorber; means for generating a selected reference signal; and flow control means including at least one electrically operated load valve connected between the absorber and a source of working fluid for controlling the fill of the absorber and one electrically operated unload valve connected to the absorber for controlling the withdrawal of fluid from the absorber, the flow control means being responsive to the difference between the torque signal and the reference signal for controlling the level of working fluid within the absorber to cause the absorber to operate at a substantially constant torque.

Claim 15

In a load control system for controlling the retarding force characteristics of a hydraulic rotary power absorber in which the absorbed torque varies in proportion to the level of fill of the working fluid, the combination which comprises: torque signal generating means for generating a signal representative of the torque absorbed by the power absorber; means for generating a selected reference signal; and flow control means including at least one electrically operated load valve connected between the absorber and a source of working fluid for controlling the fill of the absorber and one electrically operated unload valve connected to the absorber for controlling the withdrawal of fluid from the absorber, the flow control means being responsive to the difference between the torque signal and the reference signal for controlling the level of working fluid within the absorber to cause the absorber to operate at a substantially constant torque.

Claim 16

In a load control system for controlling the retarding force characteristics of a hydraulic rotary power absorber in which the absorbed torque varies in proportion to the level of fill of the working fluid within the absorber and changes substantially with the square of speed changes with a given fill, the working fluid being supplied from a source and discharged into a sink, the combination which comprises: speed signal generating means coupled to the absorber for generating a speed signal representative of the rotational speed thereof; torque signal generating means coupled to the absorber for generating a torque signal representative of the absorbed torque; flow control means connected between the power absorber, the source and the sink and responsive to the speed and torque signals for controlling the level of working fluid within the absorber to cause the absorbed torque to vary substantially as the square of the speed of the absorber; and a power select means coupled to the flow control means for adjusting the absorbed torque to a selected value at a given speed.

Claim 17

In a load control system for controlling the retarding force characteristics of a hydraulic rotary power absorber in which the absorbed torque varies in proportion to the level of fill of the working fluid within the absorber and changes substantially with the square of speed changes with a given fill, the working fluid being supplied from a source and discharged into a sink, the combination which comprises: speed signal generating means coupled to the absorber for generating a speed signal representative of the rotational speed thereof; torque signal generating means coupled to the absorber for generating a torque signal representative of the absorbed torque; flow control means connected between the power absorber, the source and the sink and responsive to the speed and torque signals for controlling the level of working fluid within the absorber to cause the absorbed torque to vary substantially as the square of the speed of the absorber; and a power select means coupled to the flow control means for adjusting the absorbed torque to a selected value at a given speed.

Claim 18

The combination as defined in claim 11 wherein the flow control means includes comparator means for comparing the torque signal with the square of the speed signal.

Claim 19

The combination as defined in claim 12 wherein the flow control means further includes at least one electrically operated load valve connected between the source of working fluid and the absorber for controlling the fill of the absorber and at least one electrically operated unload valve connected between the sink and the absorber for controlling the withdrawal of fluid from the absorber.

Claim 20

The combination as defined in claim 13 including means responsive to the speed signal for maintaining the load and unload valves closed when the speed of the absorber is below a predetermined value.

Claim 21

The combination as defined in claim 13 wherein the flow control means further includes rate control means for controlling the rate of flow through the load and unload valves in accordance with the magnitude of the difference between the torque and the squared speed signal.

Claim 22

The combination as defined in claim 15 wherein the flow control means further includes a second electrically operating load valve connected between the source and the absorber and a second eleCtrically operated unload valve connected between the sink and the absorber.

Claim 23

The combination as defined in claim 16 wherein the flow control means opens the second load and unload valves only when the magnitude of the difference between the torque and squared speed signals exceeds a predetermined value.

Claim 24

The combination as defined in claim 17 wherein the load and unload valves are arranged to open or close completely and wherein the rate control means controls the duty cycle of the first load and unload valves to provide a linearly decreasing duty cycle as the value of the torque signal approaches the squared speed signal.

Claim 25

In a dynamometer system for imposing a load on an engine or motor vehicle which simulates operating or normal driving conditions, the combination which comprises: a hydraulic rotary power absorber arranged to provide an absorbed torque which varies in proportion to the level of fill of the working fluid therein and which changes substantially with the square of speed changes with a given fill; a plurality of flywheels; means for selectively coupling one or more of the flywheels to the absorber to simulate the inertia of the engine or vehicle under test; speed signal generating means coupled to the absorber for generating a speed signal representative of the rotational speed thereof; torque signal generating means coupled to the absorber for generating a torque signal representative of the absorbed torque; power select means responsive to at least one of said speed and torque signals for providing a programmed torque output signal representative of the desired absorbed torque over a range of operating conditions; means for comparing the programmed torque signal and the absorbed torque signal and for providing an error signal representative of the difference therebetween; and flow control means connected to the power absorber and adapted to be connected to a source and sink of the working fluid and responsive to the error signal for controlling the level of working fluid within the absorber to reduce the error signal.

Claim 26

In a dynamometer system for imposing a load on an engine or motor vehicle which simulates operating or normal driving conditions, the combination which comprises: a hydraulic rotary power absorber arranged to provide an absorbed torque which varies in proportion to the level of fill of the working fluid therein and which changes substantially with the square of speed changes with a given fill; a plurality of flywheels; means for selectively coupling one or more of the flywheels to the absorber to simulate the inertia of the engine or vehicle under test; speed signal generating means coupled to the absorber for generating a speed signal representative of the rotational speed thereof; torque signal generating means coupled to the absorber for generating a torque signal representative of the absorbed torque; power select means responsive to at least one of said speed and torque signals for providing a programmed torque output signal representative of the desired absorbed torque over a range of operating conditions; means for comparing the programmed torque signal and the absorbed torque signal and for providing an error signal representative of the difference therebetween; and flow control means connected to the power absorber and adapted to be connected to a source and sink of the working fluid and responsive to the error signal for controlling the level of working fluid within the absorber to reduce the error signal.

Claim 27

The combination as defined by claim 19 wherein the power select means is responsive to the speed signal squared for providing a programmed torque signal which varies as the square of the rotational speed of the absorber.

Claim 28

The combination as defined by claim 20 wherein the flow control means includes at least one electrically operated load valve connected to the absorber and adapted to be connected to the source for controlling the flow of fluid into the absorber and at least one electrically operated unload valve connected to the power absorber and adapted to be connected to a sink for controlling the withdrawal of fluid from the absorber.

Claim 29

The combination as defined by claim 21 wherein the flow control means further includes rate control means for controlling the rate of flow through the load and unload valves in accordance with the magnitude of the error signal.

Claim 30

The combination as defined by claim 22 wherein the load and unload valves are arranged to open and close completely and wherein the rate control means decreases the duty cycle of the valves as the error signal approaches zero.

Claim 31

The combination as defined in claim 23 including a second electrically operated load and unload valve connected to the absorber and adapted to be connected to the source and sink, respectively.

Claim 32

The combination as defined in claim 24 wherein the flow control means is arranged to periodically open the first load or unload valves with a duty cycle which is substantially linear with changes in the error signal between first and second predetermined values of error signal and to open the second load or unload valves when the error signal exceeds a third predetermined value of error signal.

Claim 33

The combination as defined in claim 21 including means responsive to the speed signal for disabling the flow control means when the rotational speed of the absorber is below a preselected value.

Claim 34

In a dynamometer system for imposing a programmed torque on a motor vehicle which simulates operating or normal driving conditions, the combination which comprises; a hydraulic rotary power absorber arranged to provide an absorbed torque which varies in proportion to the level of working fluid therein and which changes substantially with the square of speed changes with a given level of fill; a drive roll connected to the absorber for imparting rotary motion thereto; an idle roll spaced from the drive roll, the drive and idle rolls arranged to support the drive wheels of a motor vehicle therebetween; a plurality of flywheels; means for selectively coupling one or more of the flywheels to the drive roll to simulate a selected inertia for the vehicle under test; speed signal generating means coupled to one of the drive and idle rolls for generating a speed signal representative of the rotational speed of the absorber; torque signal generating means coupled to the absorber for generating a torque signal representative of the absorbed torque; squaring means coupled to the speed signal generating means for providing an output signal representative of the square of the speed signal; power select means having an input connected to the squaring means to receive the squared speed signal and an output and being arranged to provide an output signal which follows a selected torque vs. speed squared curve; means for comparing the output signal from the power select means with the absorbed torque signal and providing an error signal having a polarity and amplitude representative of the difference between said signals; and flow control means including at least one load valve and one unload valve connected to the absorber and adapted to be connected to a source and sink for the working fluid, respectively, the flow control means being responsive to an error signal of one polarity for opening the load valve and responsive to an error signal of the other polarity to open the unload valve to change the absorbed torque and reduce the error signal.

Claim 35

In a dynamometer system for imposing a programmed torque on a motor vehicle which simulates operating or normal driving conditions, the combination which comprises; a hydraulic rotary power absorber arranged to provide an absorbed torque which varies in proportion to the level of working fluid therein and which changes substantially with the square of speed changes with a given level of fill; a drive roll connected to the absorber for imparting rotary motion thereto; an idle roll spaced from the drive roll, the drive and idle rolls arranged to support the drive wheels of a motor vehicle therebetween; a plurality of flywheels; means for selectively coupling one or more of the flywheels to the drive roll to simulate a selected inertia for the vehicle under test; speed signal generating means coupled to one of the drive and idle rolls for generating a speed signal representative of the rotational speed of the absorber; torque signal generating means coupled to the absorber for generating a torque signal representative of the absorbed torque; squaring means coupled to the speed signal generating means for providing an output signal representative of the square of the speed signal; power select means having an input connected to the squaring means to receive the squared speed signal and an output and being arranged to provide an output signal which follows a selected torque vs. speed squared curve; means for comparing the output signal from the power select means with the absorbed torque signal and providing an error signal having a polarity and amplitude representative of the difference between said signals; and flow control means including at least one load valve and one unload valve connected to the absorber and adapted to be connected to a source and sink for the working fluid, respectively, the flow control means being responsive to an error signal of one polarity for opening the load valve and responsive to an error signal of the other polarity to open the unload valve to change the absorbed torque and reduce the error signal.

Claim 36

The combination as defined in claim 27 wherein the flow control means varies the duty cycle of the load or unload valve linearly with the changes in the magnitude of the error signal over a predetermined range of magnitude.

Claim 37

The combination as defined in claim 28 including means responsive to the speed signal for disabling operation of the flow control means when the speed is below a preselected value.

Claim 38

In a system for controlling the retarding force characteristics of a rotary power absorber in which the absorbed torque is increased and decreased, respectively, by operation of load and unload control mechanisms, the combination which comprises: means for generating a programmed signal representative of the desired absorbed torque or speed of the power absorber, means connected to the power absorber for generating a second signal representative of the actual absorbed torque or speed of the power absorber, comparing means for comparing the programmed signal with the second signal and for generating an error signal representative of the difference therebetween, and pulse modulation control means responsive to the error signal for periodically turning the load or unload control mechanism on and off when the magnitude of the error signal is between first and second predetermined values to reduce the error signal.

Claim 39

In a system for controlling the retarding force characteristics of a rotary power absorber in which the absorbed torque is increased and decreased, respectively, by operation of load and unload control mechanisms, the combination which comprises: means for generating a programmed signal representative of the desired absorbed torque or speed of the power absorber, means connected to the power absorber for generating a second signal representative of the actual absorbed torque or speed of the power absorber, comparing means for comparing the programmed signal with the second signal and for generating an error signal representative of the difference therebetween, and pulse modulation control means responsive to the error signal for periodically turning the load or unload control mechanism on and off when the magnitude of the error signal is between first and second predetermined values to reduce the error signal.

Claim 40

The combination as defined in claim 30 wherein the pulse modulation means controls the ratio of the on to off time of the control mechanism during each period in proportion to the magnitude of the error signal.

Claim 41

The combination as defined in claim 31 wherein the pulse modulation system varies the ratio of the on to off time of the control mechanism linearly with changes in the magnitude of the error signal.

Claim 42

The combination as defined in claim 32 wherein the programmed signal is representative of the dEsired absorbed torque and the second signal is representative of the actual absorbed torque.

Claim 43

The combination as defined in claim 33 wherein the error signal is a d.c. signal and the pulse modulation means is responsive to the polarity and magnitude of the error signal for operating the load control mechanism when the error signal is of one polarity and for operating the unload control mechanism when the error signal is of the opposite polarity.

Claim 44

The combination as defined in claim 34 wherein the pulse modulation means includes means for adjusting the repetition rate of the on-off periods within a preselected range to accomodate the load-unload characteristics of different absorbers.

Claim 45

The combination as defined in claim 34 wherein the absorber is a hydraulic rotary power absorber in which the absorbed torque varies in proportion to the level of fill of working fluid within the absorber and the control mechanisms comprise electrically operated on-off valves connected between the absorber and source and sink for the working fluid to supply or withdraw fluid from the absorber.

Claim 46

The combination as defined in claim 32 wherein the programmed signal is representative of the desired speed and the second signal is representative of the actual speed of the absorber.