CA2184957A1 - Human limb load sensing device - Google Patents
Human limb load sensing deviceInfo
- Publication number
- CA2184957A1 CA2184957A1 CA002184957A CA2184957A CA2184957A1 CA 2184957 A1 CA2184957 A1 CA 2184957A1 CA 002184957 A CA002184957 A CA 002184957A CA 2184957 A CA2184957 A CA 2184957A CA 2184957 A1 CA2184957 A1 CA 2184957A1
- Authority
- CA
- Canada
- Prior art keywords
- load
- signal
- limb
- feedback
- generating
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/22—Ergometry; Measuring muscular strength or the force of a muscular blow
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/103—Detecting, measuring or recording devices for testing the shape, pattern, colour, size or movement of the body or parts thereof, for diagnostic purposes
- A61B5/1036—Measuring load distribution, e.g. podologic studies
- A61B5/1038—Measuring plantar pressure during gait
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/45—For evaluating or diagnosing the musculoskeletal system or teeth
- A61B5/4528—Joints
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
- A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
- A61B5/6813—Specially adapted to be attached to a specific body part
- A61B5/6828—Leg
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
- A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
- A61B5/6813—Specially adapted to be attached to a specific body part
- A61B5/6829—Foot or ankle
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
- A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
- A61B5/683—Means for maintaining contact with the body
- A61B5/6831—Straps, bands or harnesses
Abstract
An apparatus is used for sensing the amount of weight applied to the limb of a patient. The apparatus includes a sensor for attachment under the foot, a control unit for receiving and processing an output signal from the sensor, and an audio output for producing feedback signals to user. The apparatus generates audio feedback to the patient indicating the amount of load being applied to the limb. The audio feedback volume and frequency decrease as load increases and is attenuated to zero when the load on the sensor reaches a selectable threshold load. The apparatus also provides an audio overload alarm signal when a load exceeding the sum of the threshold load value and a selectable overload value is being applied to the limb. The apparatus is automatically calibrated to the maximum load that can be applied to the sensor, thus eliminating the need for manual calibration. The threshold load value, the overload alarm value, and the audio output volume are selectively adjustable.
Description
HUMAN LIMB LOAD SENSING DEVICE
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for monitoring the amount of weight applied to the limb of a patient, particularly 5 useful during rehabilitative therapy.
BACKGROUND
After illness or injury an individual may require rehabilitative therapy to help regain the use of an injured or atrophied limb. It is often very beneficial during therapy, particularly in the case of individuals who are 10 having problems walking or standing, to have an aid for determining the amount of weight being applied to the limb, as well as an aid for achieving the proper weight distribution between the limbs.
Devices which attach to the limb of the individual during therapy and provide audio feedback to the individual are known. These 15 devices include devices of the type having a sensor which attaches to the limb for detecting the load applied to the limb. The device communicates an audio signal to the individual indicating the load being applied. This audio signal helps the individual to apply the correct amount of weight.
Some problems are associated with this type of device. The 20 known devices often indicate when weight is applied to the limb up to a preset amount. At that level, the feedback signal cuts off. Consequently, it is possible for an individual unintentionally to apply an excessive load on a limb and become unbalanced.
The known devices also require calibration for each individual 25 before use. This often requires weighing the individual and manually adjusting settings on the device. This is time consuming and makes it difficult for an individual to use the device without assistance.
21 ~d 4957 SUMMARY
According to one aspect of the present invention there is provided a method of producing feedback signals representative of the magnitude of a load applied to a limb of a user, said method comprising:
attaching a load sensor to the limb;
applying a load to the sensor through the limb;
monitoring a load sensor output representative of the load applied to the limb;
generating a load signal representative of the load signal 1 0 output;
generating a load threshold signal representing a desired maximum load to be applied to the limb;
generating an overload signal representing an excessive load applied to the limb;
comparing the load signal with the load threshold signal;
comparing the load signal with the overload signal;
generating a load feedback signal variable with the difference between the load signal and the load threshold signal when the load signal is less than the load threshold signal; and generating an alarm feedback signal when the load signal is greater than the overload signal.
The feedback thus includes both a normal load signal for feedback when the load is within the desired range, and an overload alarm to warn when an unbalanced condition is being approached. Where the load threshold signal is less than the overload signal, no feedback signal is generated when the load is between the desired maximum load and the excessive load. The user is not then confronted with a sudden transition from the normal feedback signal to an alarm condition.
The two feedback signals are preferably an audible signals.
The load feedback signal may vary in frequency and magnitude with differences between the load signal and the load threshold signal, while the alarm feedback signal is a constant tone.
According to another aspect of the present invention there is provided a method of monitoring a load applied to a limb of a user and producing a signal that is variable in response to variations in the magnitude of the load, said method comprising:
attaching a load sensor to the limb of the user for generating a load sensor output representative of loads applied to the limb;
monitoring the load sensor output;
generating a load signal representative of the load sensor output;
applying a peak load to the limb;
detecting a peak load signal;
recording the peak load signal;
selecting a proportion of the peak load for use as a load threshold;
generating a load threshold signal equivalent to said selected proportion the peak load signal;
comparing the load threshold signal with the load signal; and generating a feedback signal representative of the difference between the load threshold signal and the load signal.
This provides for automatic calibration simply by applying the peak load to the sensor. The selection of the load threshold is based on the activity to be carried out. It may be the maximum load, or 100% for - 21 8~9~7 walking, or less for activities where loads are carried by both limbs at all times.
According to another aspect of the present invention, there is provided a limb load sensing apparatus for producing feedback signals 5 representative of the magnitude of a load applied to a limb of a user, said apparatus comprising:
a load sensor adapted to be attached to the limb of the user for producing a load sensor output representative of the load applied to the limb;
load signal generating means coupled to the load sensor for monitoring the load sensor output and for generating a load signal representative of the load signal output;
load threshold signal generating means for generating a load threshold signal representing a desired maximum load to be applied to the 1 5 limb;
overload signal generating means for generating an overload signal representing an excessive load applied to the limb;
load feedback generator means for comparing the load signal with the load threshold signal and generating a load feedback signal that varies with the difference between the load signal and the load threshold signal when the load signal is less than the load threshold signal; and overload feedback generator means for comparing the load signal with the overload signal and generating an alarm feedback signal when the load siynal is greater than the overload signal.
The apparatus is preferably configured as a sensor pad, a small control unit that can be worn on a belt and a set of headphones to provide an audible feedback. A control knob on the unit allows the overload signal 21 84q~7 to be set to represent a load applied to the limb that is a set amount above the desired maximum load.
The load signal generating means preferably vary both the frequency and amplitude of the load feedback signal.
The apparatus may also include a calibrator having a peak load responsive means for recording a peak load signal generated in response to a peak load applied to the sensor and a load threshold signal generator for selecting a proportion of the peak load signal as the load threshold signal.
This calibrates the control to a peak load applied to the sensor, recording the peak sensor output.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which illustrate an exemplary embodiment of the present invention:
Figure 1 is an illustration of the components of the apparatus;
Figure 2 is a top view of an alternative insole sensor pad;
Figure 3 is a cross sectional view of the alternative sensor pad taken along line 3-3 of Figure 2;
Figure 4 is a block diagram showing the main components of the apparatus;
Figure 5 is a partial circuit diagram showing a signal processing circuit;
Figure 6 is a partial circuit diagram showing an alarm signal enable/disable circuit;
Figure 7 is a partial circuit diagram showing a volume control and audio circuit;
Figure 8 is a partial circuit diagram showing a multiplexer and related circuitry;
21 84~57 Figure 9 is a circuit diagram of an indicator light control; and Figure 10 is a circuit diagram of a calibrator reset circuit;
DETAILED DESCRIPTION
Referring to Figure 1, a limb load sensing device 10 has three 5 basic components. These are a sensor 12 for attachment to the foot of a user, a control unit 14 for receiving and processing an output signal from the sensor 12, and a set of headphones 16 for delivering an audible feedback to the user. The control unit 14 may be carried or worn by the user, for example on a belt.
The sensor 12 is responsive to an applied load and provides an output that varies with the load applied to it by the limb. The sensor 12 comprises spaced apart electrically conductive plates 18 and a layer of non-conducting, resiliently compressible material 20 between the plates 18. The spaced apart plates 18 and compressible material 20 act as an electrical 15 capacitor. As a load is applied to the sensor 12 the resiliently compressiblelayer 20 is compressed an amount that varies with the applied load. This varies the spacing between the plates 18, varying the capacitance of the sensor 12, which is the sensor output. The sensor plates are connected to the respective conductors of a two conductor cable 24. A jack 26 is 20 connected to the cable end for electrically connecting the sensor to the control unit 14.
The sensor 12 is placed under an user's foot for use. In the embodiment of Figure 1, the sensor is equipped with straps 28 that engage around the user's foot or shoe to hold the sensor in place. The straps have 25 fasteners 30, for example the face to face fastener material sold under the trade mark "Velcro" for coupling the straps. An alternative embodiment, without straps and sized to fit within the user's shoe is shown in Figure 2.
21B4q57 The control unit 14 is a battery operated processor that requires low voltage and current. The control unit has a housing 32 of relatively small dimensions, e.g. 150mm x 75mm x 50mm. The unit has a number of external controls, including an on/off switch 34, a volume control 5 36, an overload setting control 38, a threshold load setting control 40, a sensor input connector 42, an audio output connector 44, and a battery recharger connector 46. The unit also has a battery condition LED window 47.
As shown in the block diagram of Figure 4, the output of 10 sensor 12 is input to an oscillator and divider 48. The oscillator produces an output signal with a frequency that is inversely proportional to the capacitance of the sensor 12. This output goes to a low pass filter and DC
converter 50. The filter and converter attenuates the output from the oscillator and converts it to a DC output with a voltage that varies with the 15 load applied to the sensor 12. The filter and converter output is supplied toa calibrator circuit 52. This stores the highest voltage that the converter can produce.
The calibrator voltage is applied to a percentage load adjustment circuit 54 to adjust the threshold load setting using the control 20 40 on the control unit 14.
The outputs from the percentage load adjustment circuit 54 and the DC converter 50 are supplied to a feedback control comparator 56. The output of this comparator goes negative when the output voltage from the DC converter is greater than or equal to the voltage from the threshold load 25 adjustment circuit 54. The output of the feedback control comparator 66 is used to switch the audio feedback tone on and off as will be discussed more fully in the following.
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for monitoring the amount of weight applied to the limb of a patient, particularly 5 useful during rehabilitative therapy.
BACKGROUND
After illness or injury an individual may require rehabilitative therapy to help regain the use of an injured or atrophied limb. It is often very beneficial during therapy, particularly in the case of individuals who are 10 having problems walking or standing, to have an aid for determining the amount of weight being applied to the limb, as well as an aid for achieving the proper weight distribution between the limbs.
Devices which attach to the limb of the individual during therapy and provide audio feedback to the individual are known. These 15 devices include devices of the type having a sensor which attaches to the limb for detecting the load applied to the limb. The device communicates an audio signal to the individual indicating the load being applied. This audio signal helps the individual to apply the correct amount of weight.
Some problems are associated with this type of device. The 20 known devices often indicate when weight is applied to the limb up to a preset amount. At that level, the feedback signal cuts off. Consequently, it is possible for an individual unintentionally to apply an excessive load on a limb and become unbalanced.
The known devices also require calibration for each individual 25 before use. This often requires weighing the individual and manually adjusting settings on the device. This is time consuming and makes it difficult for an individual to use the device without assistance.
21 ~d 4957 SUMMARY
According to one aspect of the present invention there is provided a method of producing feedback signals representative of the magnitude of a load applied to a limb of a user, said method comprising:
attaching a load sensor to the limb;
applying a load to the sensor through the limb;
monitoring a load sensor output representative of the load applied to the limb;
generating a load signal representative of the load signal 1 0 output;
generating a load threshold signal representing a desired maximum load to be applied to the limb;
generating an overload signal representing an excessive load applied to the limb;
comparing the load signal with the load threshold signal;
comparing the load signal with the overload signal;
generating a load feedback signal variable with the difference between the load signal and the load threshold signal when the load signal is less than the load threshold signal; and generating an alarm feedback signal when the load signal is greater than the overload signal.
The feedback thus includes both a normal load signal for feedback when the load is within the desired range, and an overload alarm to warn when an unbalanced condition is being approached. Where the load threshold signal is less than the overload signal, no feedback signal is generated when the load is between the desired maximum load and the excessive load. The user is not then confronted with a sudden transition from the normal feedback signal to an alarm condition.
The two feedback signals are preferably an audible signals.
The load feedback signal may vary in frequency and magnitude with differences between the load signal and the load threshold signal, while the alarm feedback signal is a constant tone.
According to another aspect of the present invention there is provided a method of monitoring a load applied to a limb of a user and producing a signal that is variable in response to variations in the magnitude of the load, said method comprising:
attaching a load sensor to the limb of the user for generating a load sensor output representative of loads applied to the limb;
monitoring the load sensor output;
generating a load signal representative of the load sensor output;
applying a peak load to the limb;
detecting a peak load signal;
recording the peak load signal;
selecting a proportion of the peak load for use as a load threshold;
generating a load threshold signal equivalent to said selected proportion the peak load signal;
comparing the load threshold signal with the load signal; and generating a feedback signal representative of the difference between the load threshold signal and the load signal.
This provides for automatic calibration simply by applying the peak load to the sensor. The selection of the load threshold is based on the activity to be carried out. It may be the maximum load, or 100% for - 21 8~9~7 walking, or less for activities where loads are carried by both limbs at all times.
According to another aspect of the present invention, there is provided a limb load sensing apparatus for producing feedback signals 5 representative of the magnitude of a load applied to a limb of a user, said apparatus comprising:
a load sensor adapted to be attached to the limb of the user for producing a load sensor output representative of the load applied to the limb;
load signal generating means coupled to the load sensor for monitoring the load sensor output and for generating a load signal representative of the load signal output;
load threshold signal generating means for generating a load threshold signal representing a desired maximum load to be applied to the 1 5 limb;
overload signal generating means for generating an overload signal representing an excessive load applied to the limb;
load feedback generator means for comparing the load signal with the load threshold signal and generating a load feedback signal that varies with the difference between the load signal and the load threshold signal when the load signal is less than the load threshold signal; and overload feedback generator means for comparing the load signal with the overload signal and generating an alarm feedback signal when the load siynal is greater than the overload signal.
The apparatus is preferably configured as a sensor pad, a small control unit that can be worn on a belt and a set of headphones to provide an audible feedback. A control knob on the unit allows the overload signal 21 84q~7 to be set to represent a load applied to the limb that is a set amount above the desired maximum load.
The load signal generating means preferably vary both the frequency and amplitude of the load feedback signal.
The apparatus may also include a calibrator having a peak load responsive means for recording a peak load signal generated in response to a peak load applied to the sensor and a load threshold signal generator for selecting a proportion of the peak load signal as the load threshold signal.
This calibrates the control to a peak load applied to the sensor, recording the peak sensor output.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings, which illustrate an exemplary embodiment of the present invention:
Figure 1 is an illustration of the components of the apparatus;
Figure 2 is a top view of an alternative insole sensor pad;
Figure 3 is a cross sectional view of the alternative sensor pad taken along line 3-3 of Figure 2;
Figure 4 is a block diagram showing the main components of the apparatus;
Figure 5 is a partial circuit diagram showing a signal processing circuit;
Figure 6 is a partial circuit diagram showing an alarm signal enable/disable circuit;
Figure 7 is a partial circuit diagram showing a volume control and audio circuit;
Figure 8 is a partial circuit diagram showing a multiplexer and related circuitry;
21 84~57 Figure 9 is a circuit diagram of an indicator light control; and Figure 10 is a circuit diagram of a calibrator reset circuit;
DETAILED DESCRIPTION
Referring to Figure 1, a limb load sensing device 10 has three 5 basic components. These are a sensor 12 for attachment to the foot of a user, a control unit 14 for receiving and processing an output signal from the sensor 12, and a set of headphones 16 for delivering an audible feedback to the user. The control unit 14 may be carried or worn by the user, for example on a belt.
The sensor 12 is responsive to an applied load and provides an output that varies with the load applied to it by the limb. The sensor 12 comprises spaced apart electrically conductive plates 18 and a layer of non-conducting, resiliently compressible material 20 between the plates 18. The spaced apart plates 18 and compressible material 20 act as an electrical 15 capacitor. As a load is applied to the sensor 12 the resiliently compressiblelayer 20 is compressed an amount that varies with the applied load. This varies the spacing between the plates 18, varying the capacitance of the sensor 12, which is the sensor output. The sensor plates are connected to the respective conductors of a two conductor cable 24. A jack 26 is 20 connected to the cable end for electrically connecting the sensor to the control unit 14.
The sensor 12 is placed under an user's foot for use. In the embodiment of Figure 1, the sensor is equipped with straps 28 that engage around the user's foot or shoe to hold the sensor in place. The straps have 25 fasteners 30, for example the face to face fastener material sold under the trade mark "Velcro" for coupling the straps. An alternative embodiment, without straps and sized to fit within the user's shoe is shown in Figure 2.
21B4q57 The control unit 14 is a battery operated processor that requires low voltage and current. The control unit has a housing 32 of relatively small dimensions, e.g. 150mm x 75mm x 50mm. The unit has a number of external controls, including an on/off switch 34, a volume control 5 36, an overload setting control 38, a threshold load setting control 40, a sensor input connector 42, an audio output connector 44, and a battery recharger connector 46. The unit also has a battery condition LED window 47.
As shown in the block diagram of Figure 4, the output of 10 sensor 12 is input to an oscillator and divider 48. The oscillator produces an output signal with a frequency that is inversely proportional to the capacitance of the sensor 12. This output goes to a low pass filter and DC
converter 50. The filter and converter attenuates the output from the oscillator and converts it to a DC output with a voltage that varies with the 15 load applied to the sensor 12. The filter and converter output is supplied toa calibrator circuit 52. This stores the highest voltage that the converter can produce.
The calibrator voltage is applied to a percentage load adjustment circuit 54 to adjust the threshold load setting using the control 20 40 on the control unit 14.
The outputs from the percentage load adjustment circuit 54 and the DC converter 50 are supplied to a feedback control comparator 56. The output of this comparator goes negative when the output voltage from the DC converter is greater than or equal to the voltage from the threshold load 25 adjustment circuit 54. The output of the feedback control comparator 66 is used to switch the audio feedback tone on and off as will be discussed more fully in the following.
2 1 8~
A delay circuit 58 is associated with the overload setting control knob 38 on the control unit 14. The control adjusts the delay circuit to provide a selectable overload on the sensor 12 in the range from zero to 45 Ibs.. Each quarter turn of the knob provides an increment corresponding 5 to approximately 15 Ibs.
The output from the delay circuit 58 and the output from feedback control comparator 54 are summed using a summer 60. The summed signal is applied to an alarm comparator 62 with the output of the DC converter 50. When the signal from the summer is less than or equal to 10 the output from the DC converter, the comparator provides a positive output that is used for turning on an alarm tone to indicate that the load on the sensor is too high.
A multiplexer circuit 64 is a switching circuit for turning on and off the feedback signals. The feedback signals from the oscillator are 15 delivered to the multiplexer. Alarm and load feedback signals are output to an audio amplifier 66.
The multiplexer circuit 64 provides an alarm output signal when the output from the alarm comparator 62 is positive. A load feedback output signal is provided when the output from the load feedback control 20 comparator 56 is positive. The multiplexer will pass only one of the alarm signal and the load feedback signal at a time, with the alarm signal overriding the load feedback signal.
The audio amplifier 66 receives the alarm and load feedback signals from the multiplexer 64 and provides audible alarm and load 25 feedback signals. The circuit also receives input from an audio volume control 68 coupled to the DC converter 50 to modulate the load feedback volume according to the output of the DC converter.
21 84~5;7 The audio amplifier circuit provides output to the headphones 16.
The control unit 14 includes an indicator light control circuit 70.
This indicates the battery charge level to the user using red and green 5 indicator lights.
The detailed circuit diagrams are shown in Figures 5 to 10.
Referring to Figure 5 a signal processor circuit is shown generally at 72. This includes an RC sensor input circuit 74 consisting of the sensor capacitance C3 connected in series with two resistors R11 and 10 R12. The sensor capacitance is connected to an input pin 9 of a 4060 integrated circuit oscillator 48. The resistors are connected to pins 10 and 11 respectively of the oscillator. The oscillator produces at pin 4 an output signal with a frequency that is inversely proportional to the capacitance C3 of the sensor 12. Consequently, as the load applied to the sensor 12 15 increases and the capacitance C3 is reduced, the frequency of the signal generator output increases.
The oscillator IC 48 also provides a pulsed output at pin 2, an audio feedback tone signal at pin 14, and an alarm tone signal at pin 5.
The variable frequency output from oscillator pin 4 goes to the 20 positive input of a square wave generator 76 consisting of amplifier U1 and resistors R13 and R14, which constitute a voltage divider 78. This generator converts the oscillator output to a square wave form that is delivered to a low pass filter 80. The low pass filter 80 includes resistors R15 and R16, an amplifier U2 and feedback capacitor C6. This filter 25 attenuates the square wave output from the square wave generator 76 to produce an output with an amplitude that varies inversely with its frequency. Thus, the amplitude of the output from the low pass filter 80 - ~o -increases as the load applied to the sensor 12 increases.
The signal from the low pass filter is rectified and filtered by the DC converter 82. This includes rectifier diode D4, resistor R17 and capacitor C4. The DC converter 82 coverts the square wave output from the low pass filter 80 to a solid non-oscillating DC signal output with a voltage that varies with the load applied to the sensor 12.
The DC converter output is supplied to the calibrator circuit 52. This includes diode D5, a high capacitance capacitor C5 and an output resistor R18. The output from the DC converter charges the capacitor, 10 which stores the highest voltage that the converter can produce, less a small voltage drop across the diode.
The calibrator voltage is applied to the positive input of the load adjustment circuit 54. This is a unity gain follower 84, including amplifier U4, feedback resistor R19, and variable resistor R1A. The variable resistor is used to adjust the threshold load setting using the control 40 on the control unit 14.
The outputs from the load adjustment circuit 54 and the DC
converter 82 are supplied to the feedback control comparator 56. The load adjustment circuit output is delivered to the positive input and the converter output is delivered to the negative input. The output of this comparator goes negative when the output voltage from the DC converter 82is greater than or equal to the threshold voltage set by the load adjustment circuit 54.
The output of the feedback control comparator 56is used to switch the audio feedback tone on and off as will be discussed more fully in the following.
Referring to Fi~qure 10, the calibrator 52is reset by a reset switch circuit 86 when power to the control unit 14is turned off. The reset 21 ~49~7 circuit includes a transistor switch Q7. The base of the transistor is connected to the control unit on/off switch 34 through resistor R32. The collector is connected to capacitor C5, and the emitter is connected to ~round through resistor R31. When the on/off switch 34 is switched off the 5 base of the transistor Q7 is connected to the battery through resistor R32, turning Q7 on to discharge the capacitor C5 through resistor R31. The calibrator 52 is therefore reset every time the control unit 14 is turned off.
Referring to Figure 6 there is illustrated an overload alarm circuit 88. This includes a voltage divider 90 including resistor R20 and 10 variable resistor R23. The overload setting control knob 38 on the control unit 14 adjusts the variable resistor to provide a selectable overload voltage.
This overload voltage represents a load on the sensor 12 in the range from zero to 45 Ibs.. Each quarter turn of the knob provides a voltage increment corresponding to approximately 15 Ibs.
The output from voltage divider 90 and the threshold load signal output from load adjustment circuit 54 are summed using voltage summer 60 consisting of a resistor R21 connected to the follower output, a resistor R22 connected to the voltage divider 90, an amplifier U5 with its inverting input connected to the resistors R21 and R22, and feedback 20 resistor R24. The summed voltage is inverted by an inverter U6 and applied to the negative input of the comparator 62. The output of the DC converter 82 is applied to the positive terminal of the comparator 62. When the signal from the inverter U6 is greater than the output from the DC converter 82 the comparator provides a negative voltage output, and when the summed 25 voltage output from the inverter U6 is less than or equal to the output from the DC converter 82 the comparator provides a positive voltage output. A
positive output is used for turning on an alarm tone to indicate that the load 21 84~S7 on the sensor is too high.
The multiplexer circuit 64 is shown in Figure 8. This is a switching circuit for turning on and off the feedback signals. The circuit includes a 4019 quad and/or select gate 94. The audio feedback tone signal 5 from pin 14 of the oscillator is delivered to pin 15 and the alarm tone signalfrom pin 5 of the oscillator is delivered to pin 3. Alarm and counter tone outputs are at pins 12 and 13 respectively.
The gate 94 receives input at pin 14 from the overload alarm comparator through an alarm enable/disable front end 96. This includes a 10 rectifying diode D3 and an RC filter with resistor R10 and capacitor C1. The gate 94 receives input at pin 9 from the feedback control comparator 56 through a load feedback enable/disable front end 98. This includes a rectifying diode D2 and an RC filter consisting of resistor R9 and capacitor C2.
The multiplexer circuit 64 provides an alarm output signal at pin 12 when the output from the alarm enable/disable front end 96 is positive.
A load feedback output signal is provided at pin 13 when the output from the load feedback enable/disable front end 98 is positive. The gate 94 will pass only one of the alarm signal and the load feedback signal at a time, 20 with the alarm signal overriding the load feedback signal.
The audio volume control and amplifier circuits 66 and 68 are shown in Figure 7. These circuits receive the alarm and load feedback signals from the multiplexer 64 and provide audible alarm and load feedback signals. The volume control circuit 68 includes a load signal amplifier 100.
25 A transistor Q1 receives the output of the DC converter 82 at its base through a resistor R1B. Resistor R1B is ganged with resistor R1A of the load adjustment circuit 54. The collector and emitter are connected across 21 849~7 the battery through resistors R2 and R3. The collector is also connected to the base of transistor Q2 and to ground through resistor R4. The load feedback signal from pin 13 of the multiplexer gate 94 is applied to the collector of transistor Q2 to be modulated according to the output of the DC
5 converter 82.
As load is increased on the sensor 12 the voltage output of the DC converter 82 increases. The increased voltage at the base of transistor Q1 reduces the voltage drop across the transistor and hence the voltage at the base of transistor Q2. The load feedback signal through transistor Q2 is reduced. The inverting amplifier circuit therefore generates a feedback tone output signal which is attenuated as the output voltage from the DC
converter 82 increases from zero to the threshold voltage. When the threshold level is reached, the signal to pin 9 of multiplexer gate goes negative and is cut off by diode D2, cutting of the load feedback output from pin 13.
The output from the emitter of transistor Q2 is delivered through diode D1 to a logarithmic audio pot R4 which serves as a volume control. The volume control 36 on the control unit 14 allows for the adjustment of the pot R4.
The output from the audio volume control is passed to the audio amplifier circuit 66. The audio amplifier circuit 66 includes two transistors Q3 and Q4 arranged as a darlington pair. The audio amplifier circuit 66 provides output to the headphones 16.
The audio alarm signal output from the multiplexer 64 is applied to the audio amplifier circuit 66 at the base of transistor Q3 through a resistor R6. The audio amplifier circuit thus communicates an alarm tone of constant volume to headphones 16.
2 1 8~19 ~7 The control unit 14 is powered by two 9 volt rechargeable Nicad batteries 104 (Figure 1). A 24 volt DC transformer is used for recharging the batteries 104. The charger plugs into the recharger jack 46 in the control unit 14.
The indicator light control circuit 70 is shown in Figure 9. This indicates the battery charge level to the user using a green indicator light D7 and a red indicator light D8. The green indicator light D7 indicates sufficient battery charge and the red indicator light D8 indicates low battery power when the battery charge is below a minimum acceptable level. Both the 10 green and red lights D7 and D8 are LEDs.
Battery voltage is applied to the cathode of zener diode D6 through resistor R27. The zener provides a constant voltage on the inverting terminal of a comparator U8. This voltage is the lowest acceptable battery voltage. The battery voltage is also applied to a potentiometer R58 15 connected to the non-inverting input of comparator U8. The output of the comparator is applied to the base of a PNP transistor Q5 and to the collector of an NPN transistor Q6. The collector of transistor Q5 is connected to battery voltage, while the emitter is connected through a current limiting resistor R29 to the cathode of red LED D6. The base of transistor Q6 is 20 connected to the pulsed output at pin 2 of the oscillator. The emitter of transistor Q6 is connected through a current limiting resistor R30 to the anode of green LED D7.
When the battery voltage is above the lowest acceptable voltage the voltage output of the potentiometer R58 is greater than the 25 constant voltage from the diode D6. This results in a positive voltage output from the comparator U8. The transistor Q6 receives the positive comparator output and a pulsed signal at its base. This pulses the transistor 21 849~7 Q6 on and off connecting the green LED D7 intermittently to the comparator output and pulsing the light D7.
When the battery voltage drops to the lowest acceptable operating voltage, the voltage output of the potentiometer R58 falls just below the zener voltage. This results in a zero output voltage from the comparator. This turns on the PNP transistor Q5 and applies battery voltage to the red LED D8.
In use the device 10 operates to give the user an audio feedback response to his/her weight shifting. The user will hear a feedback tone of decreasing frequency and volume as weight is applied on the sensor 12. Conversely as weight on the sensor 12 is decreased the volume and frequency of the feedback tone will increase. At the selected threshold load setting the signal will stop.
This feature will allow the user to accurately know when any desired percentage of full load (threshold load) has been reached. At the threshold load setting the audio tone will stop as the user shifts his/her weight through the threshold load. If weight continues to be applied to the sensor 12 a predetermined overload will be reached and an alarm will sound to indicate the overload condition to the user.
The device 10 is self-calibrating to the user's weight when being used, and may be reset by turning device off. Calibration is achieved by bearing the maximum load on the sensor 12 and holding it momentarily.
This feature enables the user to calibrate the device 10 quickly and automatically.
To use the device, the control unit 14 is turned on with on/off switch 34. If the green LED light D7 is on, this indicates that the battery is charged sufficiently to operate the unit. If the red LED light D8 is on then 2~ 84q57 the device must be recharged before it is to be used. The sensor 12 is strapped to the shoe 27 of user securely enough so the sensor 12 does not slip but not so it is over tight. The control unit 14 is strapped to the waist of the user, the sensor 12 is plugged into the jack 42 labeled "Sensor" and 5 the headphones are plugged into the jack 44 labeled "Phones".
When the device 10 is turned on, a tone should be heard. The user then now apply full load on the limb to which the sensor 12 is attached. This action will calibrate the device 10 to the full weight of the user.
The volume control dial 36 can be used to set the signal volume to any comfortable level of audio output. The threshold load setting dial 40 may be used to set the threshold load to any percentage of full load, and the overload setting dial 38 may be used to set the amount of weight that must be applied to sensor 12 above the threshold load before the alarm will come 15 on.
While one embodiment of the present invention has been described in the foregoing, it is to be understood that other embodiments are possible within the scope of the invention. The invention is to be considered limited solely by the scope of the appended claims.
A delay circuit 58 is associated with the overload setting control knob 38 on the control unit 14. The control adjusts the delay circuit to provide a selectable overload on the sensor 12 in the range from zero to 45 Ibs.. Each quarter turn of the knob provides an increment corresponding 5 to approximately 15 Ibs.
The output from the delay circuit 58 and the output from feedback control comparator 54 are summed using a summer 60. The summed signal is applied to an alarm comparator 62 with the output of the DC converter 50. When the signal from the summer is less than or equal to 10 the output from the DC converter, the comparator provides a positive output that is used for turning on an alarm tone to indicate that the load on the sensor is too high.
A multiplexer circuit 64 is a switching circuit for turning on and off the feedback signals. The feedback signals from the oscillator are 15 delivered to the multiplexer. Alarm and load feedback signals are output to an audio amplifier 66.
The multiplexer circuit 64 provides an alarm output signal when the output from the alarm comparator 62 is positive. A load feedback output signal is provided when the output from the load feedback control 20 comparator 56 is positive. The multiplexer will pass only one of the alarm signal and the load feedback signal at a time, with the alarm signal overriding the load feedback signal.
The audio amplifier 66 receives the alarm and load feedback signals from the multiplexer 64 and provides audible alarm and load 25 feedback signals. The circuit also receives input from an audio volume control 68 coupled to the DC converter 50 to modulate the load feedback volume according to the output of the DC converter.
21 84~5;7 The audio amplifier circuit provides output to the headphones 16.
The control unit 14 includes an indicator light control circuit 70.
This indicates the battery charge level to the user using red and green 5 indicator lights.
The detailed circuit diagrams are shown in Figures 5 to 10.
Referring to Figure 5 a signal processor circuit is shown generally at 72. This includes an RC sensor input circuit 74 consisting of the sensor capacitance C3 connected in series with two resistors R11 and 10 R12. The sensor capacitance is connected to an input pin 9 of a 4060 integrated circuit oscillator 48. The resistors are connected to pins 10 and 11 respectively of the oscillator. The oscillator produces at pin 4 an output signal with a frequency that is inversely proportional to the capacitance C3 of the sensor 12. Consequently, as the load applied to the sensor 12 15 increases and the capacitance C3 is reduced, the frequency of the signal generator output increases.
The oscillator IC 48 also provides a pulsed output at pin 2, an audio feedback tone signal at pin 14, and an alarm tone signal at pin 5.
The variable frequency output from oscillator pin 4 goes to the 20 positive input of a square wave generator 76 consisting of amplifier U1 and resistors R13 and R14, which constitute a voltage divider 78. This generator converts the oscillator output to a square wave form that is delivered to a low pass filter 80. The low pass filter 80 includes resistors R15 and R16, an amplifier U2 and feedback capacitor C6. This filter 25 attenuates the square wave output from the square wave generator 76 to produce an output with an amplitude that varies inversely with its frequency. Thus, the amplitude of the output from the low pass filter 80 - ~o -increases as the load applied to the sensor 12 increases.
The signal from the low pass filter is rectified and filtered by the DC converter 82. This includes rectifier diode D4, resistor R17 and capacitor C4. The DC converter 82 coverts the square wave output from the low pass filter 80 to a solid non-oscillating DC signal output with a voltage that varies with the load applied to the sensor 12.
The DC converter output is supplied to the calibrator circuit 52. This includes diode D5, a high capacitance capacitor C5 and an output resistor R18. The output from the DC converter charges the capacitor, 10 which stores the highest voltage that the converter can produce, less a small voltage drop across the diode.
The calibrator voltage is applied to the positive input of the load adjustment circuit 54. This is a unity gain follower 84, including amplifier U4, feedback resistor R19, and variable resistor R1A. The variable resistor is used to adjust the threshold load setting using the control 40 on the control unit 14.
The outputs from the load adjustment circuit 54 and the DC
converter 82 are supplied to the feedback control comparator 56. The load adjustment circuit output is delivered to the positive input and the converter output is delivered to the negative input. The output of this comparator goes negative when the output voltage from the DC converter 82is greater than or equal to the threshold voltage set by the load adjustment circuit 54.
The output of the feedback control comparator 56is used to switch the audio feedback tone on and off as will be discussed more fully in the following.
Referring to Fi~qure 10, the calibrator 52is reset by a reset switch circuit 86 when power to the control unit 14is turned off. The reset 21 ~49~7 circuit includes a transistor switch Q7. The base of the transistor is connected to the control unit on/off switch 34 through resistor R32. The collector is connected to capacitor C5, and the emitter is connected to ~round through resistor R31. When the on/off switch 34 is switched off the 5 base of the transistor Q7 is connected to the battery through resistor R32, turning Q7 on to discharge the capacitor C5 through resistor R31. The calibrator 52 is therefore reset every time the control unit 14 is turned off.
Referring to Figure 6 there is illustrated an overload alarm circuit 88. This includes a voltage divider 90 including resistor R20 and 10 variable resistor R23. The overload setting control knob 38 on the control unit 14 adjusts the variable resistor to provide a selectable overload voltage.
This overload voltage represents a load on the sensor 12 in the range from zero to 45 Ibs.. Each quarter turn of the knob provides a voltage increment corresponding to approximately 15 Ibs.
The output from voltage divider 90 and the threshold load signal output from load adjustment circuit 54 are summed using voltage summer 60 consisting of a resistor R21 connected to the follower output, a resistor R22 connected to the voltage divider 90, an amplifier U5 with its inverting input connected to the resistors R21 and R22, and feedback 20 resistor R24. The summed voltage is inverted by an inverter U6 and applied to the negative input of the comparator 62. The output of the DC converter 82 is applied to the positive terminal of the comparator 62. When the signal from the inverter U6 is greater than the output from the DC converter 82 the comparator provides a negative voltage output, and when the summed 25 voltage output from the inverter U6 is less than or equal to the output from the DC converter 82 the comparator provides a positive voltage output. A
positive output is used for turning on an alarm tone to indicate that the load 21 84~S7 on the sensor is too high.
The multiplexer circuit 64 is shown in Figure 8. This is a switching circuit for turning on and off the feedback signals. The circuit includes a 4019 quad and/or select gate 94. The audio feedback tone signal 5 from pin 14 of the oscillator is delivered to pin 15 and the alarm tone signalfrom pin 5 of the oscillator is delivered to pin 3. Alarm and counter tone outputs are at pins 12 and 13 respectively.
The gate 94 receives input at pin 14 from the overload alarm comparator through an alarm enable/disable front end 96. This includes a 10 rectifying diode D3 and an RC filter with resistor R10 and capacitor C1. The gate 94 receives input at pin 9 from the feedback control comparator 56 through a load feedback enable/disable front end 98. This includes a rectifying diode D2 and an RC filter consisting of resistor R9 and capacitor C2.
The multiplexer circuit 64 provides an alarm output signal at pin 12 when the output from the alarm enable/disable front end 96 is positive.
A load feedback output signal is provided at pin 13 when the output from the load feedback enable/disable front end 98 is positive. The gate 94 will pass only one of the alarm signal and the load feedback signal at a time, 20 with the alarm signal overriding the load feedback signal.
The audio volume control and amplifier circuits 66 and 68 are shown in Figure 7. These circuits receive the alarm and load feedback signals from the multiplexer 64 and provide audible alarm and load feedback signals. The volume control circuit 68 includes a load signal amplifier 100.
25 A transistor Q1 receives the output of the DC converter 82 at its base through a resistor R1B. Resistor R1B is ganged with resistor R1A of the load adjustment circuit 54. The collector and emitter are connected across 21 849~7 the battery through resistors R2 and R3. The collector is also connected to the base of transistor Q2 and to ground through resistor R4. The load feedback signal from pin 13 of the multiplexer gate 94 is applied to the collector of transistor Q2 to be modulated according to the output of the DC
5 converter 82.
As load is increased on the sensor 12 the voltage output of the DC converter 82 increases. The increased voltage at the base of transistor Q1 reduces the voltage drop across the transistor and hence the voltage at the base of transistor Q2. The load feedback signal through transistor Q2 is reduced. The inverting amplifier circuit therefore generates a feedback tone output signal which is attenuated as the output voltage from the DC
converter 82 increases from zero to the threshold voltage. When the threshold level is reached, the signal to pin 9 of multiplexer gate goes negative and is cut off by diode D2, cutting of the load feedback output from pin 13.
The output from the emitter of transistor Q2 is delivered through diode D1 to a logarithmic audio pot R4 which serves as a volume control. The volume control 36 on the control unit 14 allows for the adjustment of the pot R4.
The output from the audio volume control is passed to the audio amplifier circuit 66. The audio amplifier circuit 66 includes two transistors Q3 and Q4 arranged as a darlington pair. The audio amplifier circuit 66 provides output to the headphones 16.
The audio alarm signal output from the multiplexer 64 is applied to the audio amplifier circuit 66 at the base of transistor Q3 through a resistor R6. The audio amplifier circuit thus communicates an alarm tone of constant volume to headphones 16.
2 1 8~19 ~7 The control unit 14 is powered by two 9 volt rechargeable Nicad batteries 104 (Figure 1). A 24 volt DC transformer is used for recharging the batteries 104. The charger plugs into the recharger jack 46 in the control unit 14.
The indicator light control circuit 70 is shown in Figure 9. This indicates the battery charge level to the user using a green indicator light D7 and a red indicator light D8. The green indicator light D7 indicates sufficient battery charge and the red indicator light D8 indicates low battery power when the battery charge is below a minimum acceptable level. Both the 10 green and red lights D7 and D8 are LEDs.
Battery voltage is applied to the cathode of zener diode D6 through resistor R27. The zener provides a constant voltage on the inverting terminal of a comparator U8. This voltage is the lowest acceptable battery voltage. The battery voltage is also applied to a potentiometer R58 15 connected to the non-inverting input of comparator U8. The output of the comparator is applied to the base of a PNP transistor Q5 and to the collector of an NPN transistor Q6. The collector of transistor Q5 is connected to battery voltage, while the emitter is connected through a current limiting resistor R29 to the cathode of red LED D6. The base of transistor Q6 is 20 connected to the pulsed output at pin 2 of the oscillator. The emitter of transistor Q6 is connected through a current limiting resistor R30 to the anode of green LED D7.
When the battery voltage is above the lowest acceptable voltage the voltage output of the potentiometer R58 is greater than the 25 constant voltage from the diode D6. This results in a positive voltage output from the comparator U8. The transistor Q6 receives the positive comparator output and a pulsed signal at its base. This pulses the transistor 21 849~7 Q6 on and off connecting the green LED D7 intermittently to the comparator output and pulsing the light D7.
When the battery voltage drops to the lowest acceptable operating voltage, the voltage output of the potentiometer R58 falls just below the zener voltage. This results in a zero output voltage from the comparator. This turns on the PNP transistor Q5 and applies battery voltage to the red LED D8.
In use the device 10 operates to give the user an audio feedback response to his/her weight shifting. The user will hear a feedback tone of decreasing frequency and volume as weight is applied on the sensor 12. Conversely as weight on the sensor 12 is decreased the volume and frequency of the feedback tone will increase. At the selected threshold load setting the signal will stop.
This feature will allow the user to accurately know when any desired percentage of full load (threshold load) has been reached. At the threshold load setting the audio tone will stop as the user shifts his/her weight through the threshold load. If weight continues to be applied to the sensor 12 a predetermined overload will be reached and an alarm will sound to indicate the overload condition to the user.
The device 10 is self-calibrating to the user's weight when being used, and may be reset by turning device off. Calibration is achieved by bearing the maximum load on the sensor 12 and holding it momentarily.
This feature enables the user to calibrate the device 10 quickly and automatically.
To use the device, the control unit 14 is turned on with on/off switch 34. If the green LED light D7 is on, this indicates that the battery is charged sufficiently to operate the unit. If the red LED light D8 is on then 2~ 84q57 the device must be recharged before it is to be used. The sensor 12 is strapped to the shoe 27 of user securely enough so the sensor 12 does not slip but not so it is over tight. The control unit 14 is strapped to the waist of the user, the sensor 12 is plugged into the jack 42 labeled "Sensor" and 5 the headphones are plugged into the jack 44 labeled "Phones".
When the device 10 is turned on, a tone should be heard. The user then now apply full load on the limb to which the sensor 12 is attached. This action will calibrate the device 10 to the full weight of the user.
The volume control dial 36 can be used to set the signal volume to any comfortable level of audio output. The threshold load setting dial 40 may be used to set the threshold load to any percentage of full load, and the overload setting dial 38 may be used to set the amount of weight that must be applied to sensor 12 above the threshold load before the alarm will come 15 on.
While one embodiment of the present invention has been described in the foregoing, it is to be understood that other embodiments are possible within the scope of the invention. The invention is to be considered limited solely by the scope of the appended claims.
Claims (14)
1. A method of producing feedback signals representative of the magnitude of a load applied to a limb of a user, said method comprising:
attaching a load sensor to the limb;
applying a load to the sensor through the limb;
monitoring a load sensor output representative of the load applied to the limb;
generating a load signal representative of the load signal output;
generating a load threshold signal representing a desired maximum load to be applied to the limb;
generating an overload signal representing an excessive load applied to the limb;
comparing the load signal with the load threshold signal;
comparing the load signal with the overload signal;
generating a load feedback signal variable with the difference between the load signal and the load threshold signal when the load signal is less than the load threshold signal; and generating an alarm feedback signal when the load signal is greater than the overload signal.
attaching a load sensor to the limb;
applying a load to the sensor through the limb;
monitoring a load sensor output representative of the load applied to the limb;
generating a load signal representative of the load signal output;
generating a load threshold signal representing a desired maximum load to be applied to the limb;
generating an overload signal representing an excessive load applied to the limb;
comparing the load signal with the load threshold signal;
comparing the load signal with the overload signal;
generating a load feedback signal variable with the difference between the load signal and the load threshold signal when the load signal is less than the load threshold signal; and generating an alarm feedback signal when the load signal is greater than the overload signal.
2. A method according to Claim 1 wherein the load threshold signal is less than the overload signal whereby no feedback signal is generated when the load is between the desired maximum load and the excessive load.
3. A method according to Claim 2 wherein the load feedback signal is an audible signal.
4. A method according to Claim 3 wherein the load feedback signal varies in frequency and magnitude with differences between the load signal and the load threshold signal.
5. A method according to any preceding claim wherein the alarm feedback signal is an audible signal.
6. A method according to Claim 1 further comprising the step of calibrating the load threshold signal by:
applying a peak load to the limb;
detecting a peak load signal representative of the peak load;
recording the peak load signal; and selecting a proportion of the peak load signal for use as the load threshold signal.
applying a peak load to the limb;
detecting a peak load signal representative of the peak load;
recording the peak load signal; and selecting a proportion of the peak load signal for use as the load threshold signal.
7. A method of monitoring a load applied to a limb of a user and producing a signal that is variable in response to variations in the magnitude of the load, said method comprising:
attaching a load sensor to the limb of the user for generating a load sensor output representative of loads applied to the limb;
monitoring the load sensor output;
generating a load signal representative of the load sensor output;
applying a peak load to the limb;
detecting a peak load signal;
recording the peak load signal;
selecting a proportion of the peak load for use as a load threshold;
generating a load threshold signal equivalent to said selected proportion the peak load signal;
comparing the load threshold signal with the load signal; and generating a feedback signal representative of the difference between the load threshold signal and the load signal.
attaching a load sensor to the limb of the user for generating a load sensor output representative of loads applied to the limb;
monitoring the load sensor output;
generating a load signal representative of the load sensor output;
applying a peak load to the limb;
detecting a peak load signal;
recording the peak load signal;
selecting a proportion of the peak load for use as a load threshold;
generating a load threshold signal equivalent to said selected proportion the peak load signal;
comparing the load threshold signal with the load signal; and generating a feedback signal representative of the difference between the load threshold signal and the load signal.
8. A limb load sensing apparatus for producing feedback signals representative of the magnitude of a load applied to a limb of a user, said apparatus comprising:
a load sensor adapted to be attached to the limb of the user for producing a load sensor output representative of the load applied to the limb;
load signal generating means coupled to the load sensor for monitoring the load sensor output and for generating a load signal representative of the load signal output;
load threshold signal generating means for generating a load threshold signal representing a desired maximum load to be applied to the limb;
overload signal generating means for generating an overload signal representing an excessive load applied to the limb;
load feedback generator means for comparing the load signal with the load threshold signal and generating a load feedback signal that varies with the difference between the load signal and the load threshold signal when the load signal is less than the load threshold signal; and overload feedback generator means for comparing the load signal with the overload signal and generating an alarm feedback signal when the load signal is greater than the overload signal.
a load sensor adapted to be attached to the limb of the user for producing a load sensor output representative of the load applied to the limb;
load signal generating means coupled to the load sensor for monitoring the load sensor output and for generating a load signal representative of the load signal output;
load threshold signal generating means for generating a load threshold signal representing a desired maximum load to be applied to the limb;
overload signal generating means for generating an overload signal representing an excessive load applied to the limb;
load feedback generator means for comparing the load signal with the load threshold signal and generating a load feedback signal that varies with the difference between the load signal and the load threshold signal when the load signal is less than the load threshold signal; and overload feedback generator means for comparing the load signal with the overload signal and generating an alarm feedback signal when the load signal is greater than the overload signal.
9. Apparatus according to Claim 8 wherein the overload signal generating means comprise means for selectively setting the overload signal to represent a load applied to the limb that is a selected magnitude above the desired maximum load.
10. Apparatus according to Claim 8 or 9 wherein the load feedback signal is an audio frequency signal.
11. Apparatus according to Claim 10 wherein the alarm feedback signal is an audio frequency signal.
12. Apparatus according to Claim 11 including speaker means for generating audible load feedback and alarm feedback signals.
13. Apparatus according to Claim 12 wherein the load signal generating means comprise means for varying the frequency and amplitude of the load feedback signal.
14. Apparatus according to Claim 8 further comprising:
peak load responsive means for recording a peak load signal generated in response to the maximum load applied to the sensor; and load threshold signal generator means comprising means for selecting a proportion of the peak load signal as the load threshold signal.
peak load responsive means for recording a peak load signal generated in response to the maximum load applied to the sensor; and load threshold signal generator means comprising means for selecting a proportion of the peak load signal as the load threshold signal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002184957A CA2184957A1 (en) | 1996-09-06 | 1996-09-06 | Human limb load sensing device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA002184957A CA2184957A1 (en) | 1996-09-06 | 1996-09-06 | Human limb load sensing device |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2184957A1 true CA2184957A1 (en) | 1998-03-07 |
Family
ID=4158860
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002184957A Abandoned CA2184957A1 (en) | 1996-09-06 | 1996-09-06 | Human limb load sensing device |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA2184957A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6360615B1 (en) | 2000-06-06 | 2002-03-26 | Technoskin, Llc | Wearable effect-emitting strain gauge device |
-
1996
- 1996-09-06 CA CA002184957A patent/CA2184957A1/en not_active Abandoned
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6360615B1 (en) | 2000-06-06 | 2002-03-26 | Technoskin, Llc | Wearable effect-emitting strain gauge device |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| FZDE | Discontinued |