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Description  |
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BACKGROUND AND SUMMARY
This invention relates to a passive programmable resistance device, and,
more particularly, to a resistance device which utilizes closed loop
feedback to control the movement of an object. Such a device can be
utilized in numerous and varied fields. For example, my prior U.S. patent
application Ser. No. 949,237, (now U.S. Pat. No. 4,354,676) filed Oct. 13,
1978 describes the use of a passive programmable resistance device in an
exercise machine to control the movement of the exercise bar.
In the broadest sense, the resistance device can be used to increase
accuracy and smoothness of a process involving motion of a mechanical
system, to provide a braking or cushioning effect, or a regulated means to
dissipate mechanical energy. For example, industrial and manufacturing
procedures frequently use robotics for performing certain operations. A
passive programmable resistance device could be incorporated in a robot to
control the movement of the robot.
The invention provides a controlled programmable resistance to motion of a
mechanical system utilizing passive hydraulic components. A computer or
microcomputer is utilized to provide programmable controlled feedback to
the hydraulic components.
This system for controlling resistance does not require any active
hydraulics, such as pumps or other power sources, and requires very few
mechanical components. When using the invention in an exercise machine,
for example, the result is an inherently safe means for controlling
exercise.
The basic principle of the invention is a closed loop feedback process.
Once a specific resistive function for which the controller is programmed
has been selected, the feedback process can be broken down into steps as
follows:
1. At regular intervals input signals appropriate for the specified control
function are read by the computer or microcomputer. Signals include one
related to the force on the mechanical system and/or one related to the
position or orientation of the mechanical system.
2. If needed, velocity of the mechanical system can be calculated from
position input over time, and compensations and corrections can be made to
the input and quantities to account for non-linearity in the system and
effects of mechanical geometry.
3. Based on quantities after all corrections have been made, the computer
or microcomputer determines a feedback action to be applied to a hydraulic
control valve.
4. As a result of closed loop feedback control of the valve positon,
control of the resistive force as measured at an appropriate point on the
mechanical assembly is accom- plished.
5. The control feedback process is repeated at regular intervals, steps 1
through 4.
The function of the computer or microcomputer in this invention is that of
reading the signals related to force and/or position. From this
information, and as a result of the programmed control function, a
feedback output to the system is calculated. This feedback is then input
to the motor controlling the valve. The computer or microcomputer can thus
be viewed as a black box which performs a specified control/feedback
function.
There are other means to perform the control/feedback function not
involving computers or microcomputers. However, any of these means not
using a programmable computer device would not have the degree of
flexibility possessed by the present invention. When utilizing a
microcomputer in this invention, a level of economy can be achieved not
possible with other devices.
A central feature in the design of this invention is the feedback
algorithm. Once the input signals have been translated to numerical
quantities, calculation of the feedback takes place. In general, a
description of the feedback function is:
FEEDBACK=F (Force, Position, Time)
Different control requirements require different algorithms as do different
machine geometries and different hydraulic components. A typical control
requirement might require a resistance held to a predetermined force or
velocity. For example, a simple feedback algorithm which will control a
force begins by first determining the difference between the actual
observed force and the force which is desired:
S=k(fd-fa)
Where
S=the numerical value of the feedback output,
k=a constant,
fd=desired force,
fa=actual force.
This feedback function is a linear function where the constant k is
determined while considering the specific hydraulic and mechanical system
utilized.
A feedback function similar to the one described can be utilized to control
velocity, rather than force. To accomplish this control, desired and
actual forces would be replaced with desired and actual velocities.
Other more eloborate feedback algorithms can be developed which can better
serve specific purposes. The example given does function well and is a
useful and simple illustration of the principle.
There are a multitude of other feedback functions which can perform useful
control functions. There are certain types of useful control functions
which cannot be readily expressed with a single concise equation. An
example of one such control function is called the "stickpoint function."
A "stickpoint" control function might be defined as a control function
which at some point abruptly changes the resistance to the maximum amount.
The resistance is at a maximum for a specific period of time, after which
the resistance returns to a level dictated by the background control
function. The background control function can be any control function
regulating force, velocity, or acceleration.
Other advantages accrue from incorporating a computer or microcomputer in
the control system. For example, during those times the computer is not
engaged in the actual control and feedback activity, the processor may, as
required perform other useful activities in the system. These activities
can include recording or display of relevant data of the control process.
Note that these activities are not directly linked to the feedback process
itself. When incorporating a microcomputer in the described control
process, it also becomes possible to easily use this invention as a part
of a larger system which incorporates many more processors or sensors.
Applications which may benefit from this approach include those in
robotics and those relating to industrial processes.
DESCRIPTION OF THE DRAWINGS
The invention will be explained in conjunction with illustrative
embodiments shown in the accompanying drawing, in which
FIG. 1 is a perspective view of an exercise apparatus which includes a
passive programmable resistance device constructed in accordance with the
present invention;
FIG. 2 is a block diagram of the exercise device implemented in analog
fashion;
FIG. 3 is a block diagram of the system for controlling resistance
implemented utilizing a microcomputer;
FIGS. 4a, b and c illustrate the assignment of signals on the buses of FIG.
1;
FIGS. 5A, 5B, 5C, 5D, and a block-logic diagram of the I/O and control
module of FIG. 3;
FIG. 6 is a diagram illustrating memoray assignments;
FIG. 7 is a flow diagram of the main program used in the microprocessor of
FIG. 3;
FIG. 8 is a flow diagram showing position and velocity monitoring in
response to a shaft encoder interrupt;
FIGS. 9, 9A, and 9B are a flow diagram showing the response of the computer
program to a clock interrupt;
FIG. 10 illusrtates a passive programmable resistance device which can be
used with a variety of mechanical systems; and
FIG. 11 illustrates a typical control feedback function for force control.
GENERAL DESCRIPTION OF THE INVENTION
Referring first to FIG. 10, the numeral 400 designates generally a passive
programmable resistance device. A piston 401 is reciprocable within a
hydraulic cylinder 402. A fluid conduit 403 connects the upper end of the
cylinder to a hydraulic control valve 404, and a conduit 405 connects the
lower end of the cylinder to the valve. The valve 404 is controlled by a
motor 406 to open and close fluid flow between the conduits 403 and 405. A
conventional stepper motor has been used to control the hydraulic valve.
A pressure transducer 407 is mounted in a housing 408, and the housing is
connected to the conduits 403 and 405 by conduits 409 and 410. A check
valve is mounted in the housing at the end of each of the conduits 409 and
410 so that the pressure transducer 407 can react to the hydraulic
pressure within the hydraulic cylinder 402 regardless of the direction in
which the piston 401 is moving. The pressure transducer converts fluid
pressure information to an analog voltage which is passed to an analog
multiplexer circuit 411 and an analog to digital converter 412.
A fluid reservoir 413 is connected by conduit 414 to the conduit 405 to
compensate for the varying fluid volume inside the cylinder 402 as a
result of movement of the piston shaft into and out of the cylinder. The
reservoir also compensates for fluid leakage and temperature variations.
The analog voltage signal from the pressure transducer is converted to a
digital signal by the converter 412. The digital signal is fed to a
microcomputer system 416, which is conventional. The microcomputer
includes a processor, a read only memory (ROM), a random access memoray
(RAM), and interfaces.
Another signal is fed to the microcomputer which is related to the position
of the mechanics. In the present system this signal is generated by a
potentiometer 417 whose shaft is linked to the external mechanical
assembly which is connected to the piston 201. This signal is thus also
related to the position of the piston in the cylinder. The mechanical link
between the potentiometer and the piston is not shown in FIG. 1.
Both the position and pressure signals in this embodiment of the invention
are analog voltages. However, they need not be limited to this. The
position of the mechanics could, for example, be generated by a rotary
shaft encoder with a digital output.
In the embodiment illustrated in FIG. 10, these two input signals are
multiplexed through a multiplexer 411 to a single analog to digital
converter 412. A single analog signal the microcomputer 416. The selected
signal is converted to a digital form by the analog to digital converter
412. The operation of the analog to digital converter is also controlled
by the microcomputer.
Under control of the microcomputer, data from the tranducers 408 and 417
enters the microcomputer via an interface from the analog to digital
converter. The analog inputs enter a feedback algorithm which generates an
output feedback. In the present embodiment of the invention, this output
consists of digital control signals to the stepper motor 406 which
controls the valve 404. The direction of travel for the stepper motor and
the number of motor steps in the given direction make up the entire
feedback to the hydraulic system. A motor controller 418 translates the
outputs from the microcomputer to the voltage level required for proper
motor function.
If the stepper motor is moved in the direction which causes the hydraulic
valve to restrict fluid flow, then the resistance to movement of the
piston is increased. If the stepper motor is moved in the direction which
opens the hydraulic valve, then resistance to movement of the piston is
decreased.
FIG. 11 illustrates a typical control feedback function using an
information flow diagram. This flow diagram describes a feedback loop for
force control. This flow diagram shows the time order of events in the
feedback control as well as some of the decision logic. This type of
feedback computation process is typical of a number of control functions
of which the system is capable.
The feedback routine is executed at regular intervals. Once values for
position and/or pressure are available to the microcomputer, the raw input
can be scaled through multiplication by a constant, and any offset can be
added. At this point velocity of the external mechanical system can be
calculated from the position information at present and the position
information from the previous time interval.
Any compensations for non-linearities anywhere in the system can be
performed on the data at an appropriate time in the process. For example,
one variation which must be considered is the different effective area the
cylinder exerts on the fluid depending on the direction of travel of the
piston. This is as a result of the location of the shaft on one side only
of the piston.
Once all compensations have been performed, the feedback operation can
occur. In this example, if the measured force equals the desired force, no
feedback occurs through this cycle. If the actual measured force is
greater than the desired force, the valve will close a calculated number
of steps. If the actual measured force is less than the desired force, the
valve is opened a calculated number of steps, as determined by the
feedback algorithm. When the feedback operation has been completed, other
activities required for the application can occur. These activities may
occupy the processor until the next set of data is ready to be processed.
Variations of the invention can include use of a rotary hydraulic actuator
in place of a cylinder. Such a substitution will have the same feedback
loop structure, but will directly provide means to regulate resistance to
rotary motion.
Numerous substitutions can also be made with the various elements of the
system mentioned while still adhering to the same control process. For
example, the position potentiometer could be replaced with a rotary shaft
encoder, or the stepper motor controlled valve could be replaced with a
solenoid valve, or the pressure transducer on the cylinder could be
replaced with a load cell elsewhere in the mechanical system. These and
other variations do not alter the control feedback process which is the
subject of this description.
DETAILED DESCRIPTION OF THE INVENTION
A more detailed description of the invention will now be set forth with
respect to a specific mechanical system, namely, an exercise apparatus.
Referring to FIG. 1, a set of movable handles 11, hereinafter sometimes
referred to as an exercise bar, are rotatably disposed on a frame 13. The
frame 13 has a fixed portion comprising four vertical shafts 12 secured to
the base 10 and a movable portion 14 on which the exercise bar 11 is
mounted. The exercise bar 11 supported on a base 10 has grips 16 by means
of which a person doing exercises can grip the device to act against the
force of a hydraulic cylinder and piston unit 15 which has its one end 17
rigidly secured to a strut 20 on movable frame 14 and its other end
rigidly secured to the rotatable exercise bar 11. Movable frame is mounted
to the shafts 12 using six oil impregnated bronze bearings 22. Up and down
movement of frame portion 14 is by means of a threaded shaft 24 and
threaded bearing 26. A drive motor 50 mounted to a support structure
supporting shafts 12 and 24 drives shaft 24. This permits locating the
exercise bar 11 for various exercises and adjusting it for the height of
each individual. The amount of force which must be applied at the grips 16
is determined by the setting of a valve 21 in the cylinder. In prior art
devices, such a valve was pre-set and the amount of force thereby
determined. Any resetting of the force required a manual resetting of the
valve. However, in accordance with the present invention, there is
provided, coupled to the bar 11, preferably at its point of rotation about
the shaft 23, an angle transducer 25 which provides an output
representative of the angular position of the bar 11. Mounted on the
cylinder 19 is a pressure transducer 18. Outputs from the angle transducer
25 and pressure transducer 18 are inputs to a computer 27 which in turn
provides an output to drive means 29 for positioning the valve 21. In this
manner, the computer can be preprogrammed to control the force which must
be applied at the handles 15 is almost any manner desired. For example,
the valve can be controlled to maintain a constant force, constant
velocity, or constant acceleration. Similarly, it can be programmed for a
variable force as a function of angle. Some of the various possibilities
will become more evident from the discussion below.
FIG. 2 illustrates a simplified form of the present invention. As indicated
previously, there is coupled to the exerciser bar 11 an angle transducer
25 and a force transducer 18. The valve is controlled by a stepper motor
29; this could instead be a servo motor. Furthermore, although FIG. 1
illustrates hydraulic control, control utilizing various types of motors,
particularly those with a friction drive is also possible. The angle
transducer 25 may be, for example a potentiometer and the force transducer
18 a pressure transducer each of which provide an output voltage
proportional to angle and force, respectively.
In the simple embodiment shown in FIG. 2, programming is carried out by
means of a setting means 24 and a switch having sections S1A and S1B, at
the input and output, respectively of the computing module 27. For
example, the setting means may comprise a potentiometer. Shown are the
possibilities of settings for an acceleration, velocity or a force,
whichever is desired. The angle input to the computing means 27 is
differentiated once in a differentiator 28 to obtain a velocity signal and
then differentiated again in a differentiator 30 to obtain an acceleration
signal. The input labelled A, for acceleration, is compared or summed with
the acceleration signal at a summing junction 34. Similarly, the input V
is summed at a summing junction 32 with the actual detected velocity and
the input F summed with the force input in a summing junction 36. The
results of this are fed out through the switch section S1B as an input to
the stepper motor 29. The stepper motor 29 will naturally have means
associated therewith to convert a voltage signal into a stepper motor
position. Alternatively, as noted above, the stepper motor can be replaced
by a linear servo system. With this arrangement, which would preferably
also include amplifiers and possibly some function generators to take care
of non-linearities, the motor 29 is controlled in a manner so that the
actual acceleration, velocity or force equals the desired acceleration
velocity or force as set in at the setting means 24. Feedback to the user
can be provided by meters 36a, b and c coupled to the force, velocity and
acceleration signals respectively to give him instant feedback so that he
can determine whether or not he is meeting the requirements he set for
himself at the setting means 24.
Naturally, this system only gives the capability of providing constant
force, velocity or acceleration. However, it can be expanded in such
manner that it is possible to set in a velocity, force or acceleration
profile. Naturally, such will require additional components. For example,
a plurality of programming resistors, providing different voltages along
with appropriate switching means operated as a function of angle can be
used. However, in order to get the desired flexibility and to be able to
provide operation both with constant input parameters and variable
parameters, it has been found that computing means in the form of a
microprocessor are preferable. Such gives almost unlimited flexibility
both with respect to the types of exercise profiles which can be
programmed and with the ability to provide information to the user and,
for that matter, to others who may wish to monitor him, along with
providing the ability to make a permanent record of his performance for
further analysis. Such a system is illustrated in block diagram form by
FIG. 3.
FIG. 3 is a block diagram of one system constructed according to the
present invention. The computer comprises a microcomputer which includes
an I/O and control module 31, a microprocessor module 33, a read-only
memory 35, and a random access memory 37, interconnected by means of a
common data, address and control bus 39 with the memory connected to a
memory bus 40 having some lines in common with bus 39. The I/O and control
module 31 receives inputs from the pressure transducer 18, the angle
transducer 25, for example, a shaft encoder and provides outputs to the
drive 29, for example, a stepping motor. The system also receives inputs
from a key pad 41 which permits the user to set in the type of exercise he
desires and provides outputs to an alpha-numeric display 43 to aid in the
interaction of the user with the computer. Power supplies 45 and 47 are
provided, along with a power regulator 49 coupled to the output of power
supply 47 to supply the various voltages needed in the system. Although,
various elements can be used, it has been found that a pressure transducer
model AB from Data Instruments, Inc. works well as pressure transducer 18.
Similarly, the shaft encoder may be one made by Theta Instruments under
the part No. 05-360-1 which outputs 360 pulses per revolution. Because
the nature of the exercise bar 11 is such that the hydraulic cylinder will
allow it to go to its lowest position when it is released, on start up,
the computer can determine that the device is in the initial position, and
thus the only information required from the shaft encoder are pulses
indicating an angular change. This information can then be counted or
integrated within the computer to keep track of the exact angle. The
particular stepping motor used is one available from Superior Electric
which comes equipped with a translator for converting 12 volt pulses into
proper drive signals for the motor. This type of device operates by
receiving counter-clockwise and clockwise pulses as required with the
translator converting the pulses into position signals.
Also shown on FIG. 3 is a data terminal 51 which can be plugged into the
micro-processor module 33 to permit printouts and plotting of information.
The particular microprocessor used in a Motorola 6800 .mu.P one processor
board obtained from Wintek Corporation. The read-only memory used is an
E-Prom 16 K module also from Wintek. The random access memory is a 4K RAM
module obtained from Atwood Enterprises and the I/O control module one of
special design to be discussed in detail below. The key pad 41 is a 16-key
key pad available from Cherry. Also provided is an audio alarm 53
manufactured by Mallory. This is what is sold by Mallory as Sonalert, and
is used for attracting the user's attention. It should be noted, that
although specific microcomputer components from various manufacturers have
been used herein, that other microcomputer components can equally well be
utilized.
FIGS. 4a, b and c illustrate the various signals which are carried on the
data, address and control bus. FIGS. 4-6 are explained in detail in the
aforesaid U.S. patent application Ser. No. 949,237, and this description
is incorporated herein by reference. FIG. 5 illustrates the I/O module 31
along with some of the modules with which it communicates.
The output of the pressure transducer is provided as an input to an analog
to digital converter 107 which converts the analog signal from the
pressure transducer to a digital output. The analog to digital converter
107 also supplies the necessary voltages to the pressure transducer.
Analog to digital converter 107 provides 10 data lines of output. It also
accepts a start signal which starts a conversion, a certain period of time
after which the result is available at the output. In the present system,
the timing for the conversion is done in the computer so that a
pre-determined period of time, e.g., 6 milliseconds, after a start signal
is given, data is read out. The data from analog to digital convertor 107
is an input to a peripheral interface adaptor 109. Also, communicating
with this port is the key pad 41. The key-pad has 16 keys which simply
make a closure between a common and a given line, with the common
connected to ground. The 16 outputs of the key pad are coupled into two
priority encoders 111 and 113. The encoders need not have the priority
feature, but in the present case these were the most convenient to use.
Each of the priority encoders converts 8 inputs into a 3-bit code. The
outputs of the two encoders 111 and 113 are cascaded in NOR Gates 115
through 118. The result of this conversion is a four-bit code, the outputs
of which are designated K0, K1, K2 and K3. These are inputs to the
input/output port 109. The output of gate 115 is used to simply indicate
that a key has been pressed.
The shaft encoder provides outputs on two lines, the outputs being
90.degree. out of phase with each other. These outputs are inputs to
comparators 119 and 121. The shaft encoders produce a signal which is
roughly a sine wave with a minimum of about 50 millivolts and a maximum of
about 150 millivolts. Comparators 119 and 121 shape the sine wave into
square waves with the proper voltages and polarities. The output of each
of the comparators 119 and 121 is coupled through a buffer 123 or 125
respectively. The output of the buffer 123 is coupled into a one-shot
multi-vibrator 127 which responds to a positive going pulse and the output
of the buffer 125 into a one-shot multi-vibrator 129 which responds to a
negative going pulse. The output or buffer 125 is also provided as one
input to an AND gate 131 and as one input to an AND gate 133, at the
inputs of one-shot multi-vibrators 135 and 137 respectively. The second
input of gate 133 is the output of the one-shot 127 and the second input
of Gate 131 the output of the one-shot 129. One-shots 127 and 129 give a 1
micro-second wide pulse. This in effect decodes the outputs of the shaft
encoder so that an output will appear from one-shot 135 for a clockwise
pulse and out of one-shot 137 for a counterclockwise pulse. The two
signals are Ored in a gate 139 to provide an output which indicates simply
that an encoder pulse has occurred.
In the lower right-hand corner of FIG. 5E is the circuitry for driving the
stepper motor. The stepper motor receives output from buffers 175 for a
clockwise step and 177 for a counterclockwise step. The signals being
output are the inverted signals. These signals are obtained from one shot
multi-vibrators 179 and 181, respectively. The inputs to the
multi-vibrators are through AND gates 183 and 185, respectively. Each of
the AND gates has an inverted input which receives as an enabling input
signal the signal SEL13.
With reference to the FIG. 4, it can be seen that SEL13 is used to select
input/output and that the addresses assigned to the clockwise and
counterclockwise outputs are D010 and D020. This corresponds to the
address bits A4 and A5. Thus, the address bit A4 is coupled through a
buffer 187 as a second input to the gate 183 and A5 through a buffer 189
as a second input to gate 185. The one shots are adapted to generate a 200
microsecond pulse which is the input to the translator associated with the
stepper motor.
From FIG. 5 it can be seen that the signal SEL13 is used to select the I/O.
Going then to Table A, it is seen that the addresses D008-D00B are
assigned to PIAO. DIAO is the adaptor 109. This system has the capability
of accepted additional PIAs which are not presently installed.
The remainder of the system, i.e., the microprocessor, which basically uses
Motorola components, along with the memories, are connected in
conventional fashion.
The manner in which the system operates can best be understood with
reference to the flow charts of FIGS. 7-9.
Operation is started in the main program shown on FIG. 7 by pressing a
hardware reset button as indicated in block 201. This pulls the reset line
low, causing the restart address to be generated. It is assumed that the
test/normal switch 159 of FIG. 3 is in the normal position. The first
thing done is to initialize the variables as indicated by block 203. The
program then enters a decision block 205 which asks if instructions should
be displayed. This question is put on the alphanumeric display and asked
to the user. If the user answers "yes", a block 207 is entered and
instructions are displayed. This is done on the 20 character display and
is scrolled using conventional techniques. The keyboard includes keys
labelled 0 through 9, yes, no, enter, rub out, start and stop. If in
response to the question "display instructions?", the user wanted
instructions, he would hit "yes" and as indicated by block 207, the
instructions would be displayed. The attached program and the flow chart
of FIG. 7 are set up to permit controlling force or velocity. It should be
noted that the system can also be programmed to control other parameters
such as distance and acceleration. Once the instructions are displayed,
which instructions give the user general information about the machine, or
if the user, being familiar with the machine did not ask for instructions
to be displayed, a decision block 209 is entered. Here the user is asked
whether he wishes to control force or velocity. In addition, the program
will ask information concerning what velocity and what force is desired.
The attached program is set up to handle a constant force, constant
velocity or a variable force and variable velocity in which the beginning
value and ending value are specified. Reference to the program will show
the exact questions that are asked. Specifically, the exercises just
mentioned are given numbers so that the user is asked "Exercise number?",
he can select Exercise 1, 2, 3 or 4. If he selects the exercise where he
specifies initial force and final force, then those questions will be
asked. Otherwise, if he selects constant force, he will only be asked for
one number. Similarly, he can select a single velocity or initial and
final velocity.
Continuing with the flow diagram of FIG. 7, if velocity is selected then,
in accordance with block 211, there is stored in memory an array of
desired velocity versus angle. Thereafter, in block 213 the mode is set
equal to 2 indicating velocity mode. Similarly, if force is selected, in
accordance with block 215, an array of desired force verses angle is
stored and the mode is set to 1 in accordance with block 216. Included
within the system are also measured force and measured velocity arrays. In
accordance with the next block 217, these are zeroed or reset. At this
point, instructions are given to the user that he may start the exercise;
the specific instructions are set out in the program. During exercising,
current force, angle and velocity are displayed as indicated by block 219.
After exiting this block, the program goes into a decision block 221 which
asks if stop has been pressed. The exerciser has been told to press stop
when he is finished. If he does not press stop, the program keeps looping
back through block 219. Once stop has been pressed, a decision block 223
is entered, at which point the user is asked if he wants a plot. As noted
above, the system can interface with any standard terminal. If a plot is
selected, the answer is yes and the block 225 is entered. Here the user is
given the choice of selecting a plot of desired force, measured force,
desired velocity or measured velocity. This block is exited and the plot
is displayed as indicated by block 227. The program exits from there back
to the decision block 223 to see whether another plot is desired. When it
is desired to do another exercise, hardware reset is pressed in accordance
with block 201 and the program is gone through again. It should be noted
that although the present program is set up to handle constant forces and
velocity or linearly changing forces and velocities, the capability is
present to construct an arbitrary force or velocity curve. Similarly,
other programs which provide constant or variable acceleration or which
control the ranges of movement are also possible. For example, to generate
a velocity which is variable with angle, it would only be necessary to
input into each of the locations of the desired velocity array, a velocity
desired at that angle. As presently set up, there are 120 locations in the
array, each representing a half-degree in position, giving a range of
roughly 60.degree.. The information used for the plot of measured force
and measured velocity is obtained from the measured force and measured
velocity arrays which have a value recorded therein every half-degree. The
program is presently set up so that four cycles of the exerciser are
averages for plotting purposes. Thus, normally after setting in the
desired parameters, the person doing the exercise will go through the
exercise four times before asking for a plot. A single cycle is not used
because cycles can vary quite a bit from one to the other and it is felt
that average values are better. Another possibility is loading into the
desired velocity or desired force curve what has been measured in the
measured force or measured velocity curve.
For example, if an athlete is trying to develop a certain type of motion
for a certain sport, someone who is an expert in that sport can perform
that movement on the exercising machine. His movement can then be stored
and a trainee can then be asked to operate the machine using that stored
information. This would then permit him to maximize the development of his
muscles to obtain a velocity profile which would be most helpful in that
particular sport. Other possibilities include additional programs to
examine the measured velocity and force curves after each four exercises
to determine whether or not the exerciser is tiring and to automatically
decrease the severity of the exercise in accordance therewith. This
permits exercising until completely fatigued. For example, if the
exerciser initially set in a 50 pound force and after four cycles his
velocity had slowed down considerably, the program could automatically
reduce the force to 40 pounds and so on, permitting the exerciser to work
against less and less force as he tired to get the maximum benefit from
exercising. In contrast thereto, with present systems, for example, with
weights, it would be necessary to change the weights in order to do this.
As noted above, during the exercising the measured force and velocity is
displayed along with the current angle. This gives immediate and positive
feedback to the user and permits him to know immediately whether he is
maintaining the force which he has set in for himself.
One important aspect of the system of the present invention is that it is
impossible to have a force harder than the exerciser is pushing. The way
the unit operates is that if the user is exerting, for example five pounds
and he should be exerting twenty pounds, the hydraulic valve is closed
down so that the user cannot use the bar unless he exerts th | | |
