WO2000068642A9

WO2000068642A9 - Apparatus for determining the speed of travel and distance travelled by a user

Info

Publication number: WO2000068642A9
Application number: PCT/IB2000/000583
Authority: WO
Inventors: Gerhard Stephanus Mynhardt
Original assignee: Gerhard Stephanus Mynhardt
Priority date: 1999-05-06
Filing date: 2000-05-05
Publication date: 2001-06-21
Also published as: WO2000068642A3; WO2000068642A2; AU4308600A

Abstract

Apparatus for determining the speed of travel and the distance travelled by a user comprises a GPS receiver (2) for calculating the position and speed of movement of the user and a sensor (6) which detects movement of the user and generates a movement signal. A processor receives a position/speed signal from the receiver (2) and uses it to calculate the distance travelled by the user from a given position, and uses the movement signal to verify that the calculated distance travelled and the measured speed of movement of the user correspond to actual movement of the user. In a second embodiment, first (32) and second (34) transponders are provided for attachment to the user's limbs, typically the user's ankles, and transmit signals to one another. The transponders (32, 34) transmit an accurately timed sequence of signals to one another, and variations in the time of flight of the signals are processed to determine the speed of movement and distance travelled by the user.

Description

APPARATUS FOR DETERMINING THE SPEED OF TRAVEL AND DISTANCE TRAVELLED BY A USER

BACKGROUND OF THE INVENTION

THIS invention relates to apparatus for determining the speed of travel and distance travelled by a user. The apparatus will typically be used by an athlete to determine his/her running or walking speed and the distance travelled from a starting point.

When training, athletes often need to know about a variety of parameters which will affect their performance. Examples of these parameters are speed of travel, distance travelled, step rate, step distance and heart rate.

Existing pedometers use a shock sensor to record each step that is taken. These pedometers require the distance per step to be entered into the pedometer before the athlete begins a run or walk, and the pedometer will then use this distance per step and the frequency ofthe steps to calculate the speed and distance travelled by the athlete. However, as the size ofthe athlete's step will usually vary during the course ofthe run or walk, the pre-entered step size leads to inaccuracies in the measurements.

It is therefore an object of the invention to provide apparatus for more accurately determining the speed of and distance travelled by a user, particularly a runner or walker. SUMMARY OF THE INVENTION

According to the invention there is provided apparatus for determining the speed of travel and the distance travelled by a user comprising:

a GPS receiver for receiving data signals and using the data contained therein to calculate the position and speed of movement of the user and for generating a position/speed signal corresponding thereto;

a sensor for detecting movement of the user and generating a movement signal when movement is detected; and

processor means for receiving the position/speed signal from the receiver and the movement signal from the sensor, the processor means using the position/speed signal to calculate the distance travelled by the user from a given position and the movement signal to confirm that the calculated distance travelled and speed of movement of the user correspond to actual movement ofthe user.

The sensor may be a shock sensor arranged to detect each step ofthe user.

The apparatus may include a display for displaying parameters to the user including at least one of the user's speed, distance travelled since a start time and time elapsed since a start time.

The processor means will typically be a microprocessor and the apparatus will include input means arranged to allow a user to input commands to the microprocessor.

The apparatus may include a sounding device operable by the microprocessor when the user is travelling at a speed above or below a predetermined speed range.

The apparatus may also include an altitude sensor.

The apparatus may further include communication means for communicating with a heart rate monitor.

Preferably, the apparatus includes a memory device for storing data relating to predetermined user defined parameters and a communication device for downloading the stored data to an external device.

The data may be, for example, the user's speed, the user's heart rate, the altitude and/or the distance travelled by the user.

Further according to the invention thre is provided apparatus for determining the speed of travel and the distance travelled by a user comprising:

a first transmitter connectable to a first limb of the user, the first transmitter being adapted to transmit a plurality of signals; a second receiver connectable to a second limb of the user, the second receiver being adapted to receive the plurality of signals transmitted from the first transmitter; and processor means connectable to the receiver, wherein the processor means in arranged to calculate the time taken for the plurality of signals to travel from the first transmitter to the second receiver to calculate the distance between the first transmitter and the second receiver and thereby determine the speed of travel and the distance travelled by the user.

The processor means is preferably arranged to measure differences in the time taken for the plurality of signals transmitted by the first transmitter to be received by the second receiver due to changes in the distance therebetween.

The first transmitter may include an associated first receiver and the second receiver may include an associated second transmitter.

Preferably, the first transmitter and first receiver comprise a first transponder and the second transmitter and second receiver comprise a second transponder.

The apparatus may include a sensor for detecting movement ofthe user.

The sensor is preferably a shock sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure 1 is a circuit block diagram of the main unit of a first embodiment ofthe invention; Figure 2 is a circuit block diagram of the main unit of a second embodiment ofthe invention;

Figure 3 is a circuit block diagram showing the relationship between two transponders, a transmitting circuit and the main unit illustrated in Figure 2 above;

Figure 4 is a circuit block diagram of one of the transponders illustrated in Figure 3 above;

Figure 5 is a circuit block diagram of the transmitting circuit illustrated in Figure 3 above;

Figure 6 shows the transponders connected to the shoes of a user; and

Figure 7 shows the main unit of both embodiments worn by the user.

DESCRIPTION OF EMBODIMENTS

The main purpose of the present invention is to determine accurately the speed of travel and distance travelled by a user.

It will be understood that although the invention will typically find application in the training of road and off-road runners, it can also be used by hikers and walkers, as well as by runners during track competitions, and possibly in other applications.

In a first embodiment, the invention is implemented using a receiver in the form of a Global Positioning System (GPS) receiver in conjunction with a shock sensor system.

By way of background information, the Global Positioning System was developed by the United States Department of Defence for its own use, but it was subsequently made available for commercial purposes. The system consists of approximately 21 satellites, plus three back-up satellites, placed in predictable orbits around the earth. Using these satellites, the GPS is able to provide continuous positioning information. It consists of a Space Segment (the satellites) and a Control Segment (a network of tracking stations which monitor and control the GPS satellites in orbit).

The GPS works on the principle of triangulation. Using the known distance from three or more satellites to a GPS receiver, the GPS receiver calculates its position by solving a set of equations. Information from three satellites is needed to calculate longitude and latitude at a known elevation, while information from four satellites is needed to include altitude as well. Changes in position over time provide speed information. The satellites orbit the earth twice a day continuously broadcasting their position and the time. The time on board each satellite is kept by very accurate atomic clocks.

Basically, the distance from satellite to receiver can be derived by multiplying the time it takes for the signal to arrive at the receiver based on the known propagation delay of light. Additional calculations are used to compensate for the relatively inaccurate receiver clocks, and variations in signal reception caused by upper atmospheric conditions and solar disturbances. Because the GPS was designed for military use, it contains a number of features to limit its accuracy for commercial applications. Each satellite broadcasts two signals, the first using a "C/A-code" for commercial use and the second a "P-Code" for very accurate military applications. A restriction to the commercial use of the GPS system is Selective Availability (SA). Here the data transmitted by the satellites contains deliberate errors for all but authorized military receivers. If SA is turned on, the accuracy of commercial receivers is about 100 meters, with a degree of jitter in location and speed information. For example, even when not moving, the receiver may indicate that its location has changed.

Although it is possible to substantially correct this problem using two receivers in a differential mode, in this embodiment of the invention differential GPS correction was not used due to the variations in methodology used to obtain differential correction data in different parts of the world. Instead, a sensor for detecting movement of the user in the form of a shock sensor 6 is used to provide further information regarding the user's movement, as well as the user's step pace. This is described in more detail below.

Referring now to Figure 1, which shows the electronic circuitry of the first embodiment of the invention in block schematic form, the GPS receiver module 2 can be, for example, an Ashtech G8 GPS receiver module. This is a compact module using a Philips Semiconductor manufactured GPS chipset, being the UAA1570 RF front end, and the SAA1575 base band processor. An active antenna 4 is used, which provides amplification of the received signal via a Low Noise Amplifier (not shown).

The circuit includes processor means 8 which is in the form of an integrated Motorola MC68HC05L25 microprocessor which contains its own internal program memory, read/write data memory, LCD display interface, clock and external interfaces. A sequence of program instructions (the program) is loaded into the microprocessor's program memory which executes the tasks allowing it to function. The microprocessor has two analog to digital inputs 10, which are used for the shock sensor 6 output pulses and an output of an altitude sensor 12 respectively. The altitude sensor is optional and can be excluded if so desired.

The microprocessor 8 receives speed data and position data from the GPS receiver 2, and if the device is in an active mode, it calculates distance travelled using this data. The output of the shock sensor is used to determine when the user is actually walking or running, and what the time per step is. This allows the processor to ignore any speed indications other than zero if the user is not moving, and to calculate the average speed if the user is moving at a steady pace. Thus the shock sensor 6 is used to correct for the GPS reader's occasional fluctuating readings, and thereby to provide a more accurate measurement of the speed of and distance travelled by a user.

In the prototype apparatus, a piezo film based shock sensor was used to detect the user's steps. The sensor has a small mass fixed to a top plane, and is preferably mounted in a housing on the user's body in such a way that it is most sensitive to steps taken. Alternatively, micro-machined silicon structure based shock sensors, such as those supplied by Analog Devices, can be used.

The shock sensor output signal is amplified by an operational amplifier B2, which in the prototype was a low power, low voltage TLC3702 operational amplifier, providing a positive-going pulse at each step. This pulse is sensed by the microprocessor 8 via its second analog to digital convertor input, and allows the microprocessor to detect actual movement of the user, and the period between successive steps. This allows the microprocessor to correct the GPS -based movement rate if short term variations in speed are indicated by the GPS receiver due to Selective Availability causing location, and hence speed, jitter.

A reader skilled in the art will appreciate that any other form of movement sensor could be used in conjunction with the GPS system.

The optional altitude sensor 12 uses a pressure sensor, such as the Motorola MPX7100AP differential pressure sensor, to detect differences in pressure between sea level and a current level. The differential pressure output signal is amplified by a second operational amplifier Bl, and applied to the first analog to digital converter input on the microprocessor 8. The pressure signal is then used by the microprocessor 8 to calculate altitude.

A low frequency receiver 18 detects signals containing low frequency heart rate pulses, such as the signals outputted by a Polar (trade mark) heart rate monitor. The low frequency receiver 18 uses a tuned ferrite based inductor 20 and a capacitor 22 to detect the short bursts of a carrier signal, such as a 5kHz carrier signal, for every heart beat. The detected signal is amplified by an operational amplifier B5. This circuitry may be excluded from certain versions of the unit where it is preferable to keep the cost of the unit as low as possible.

The speed and distance travelled by the user are displayed on an LCD display 14. Typically, speed, distance travelled since start and time elapsed since start are continuously displayed. The display can also be switched to display other information such as step rate/distance, time per km/mile, time/distance to reach desired completion time, etc. Speed, distance and altitude changes can also be user selected to be displayed in either metric or imperial measurements. In addition, the average speed for the active cycle, the slowest speed and the maximum speed can also be calculated and displayed on demand. The LCD display 14 contains a display of 6 digits for showing either the elapsed time or distance as selected by the user, 3 digits for displaying speed, and icons indicating aspects such as km/miles, active cycle in operation, etc. It will be appreciated that any combination of information can be displayed depending on the user's preference, and the invention is therefore not limited to only displaying the abovementioned parameters. In addition, in cases where a user requires simplicity, some of the abovementioned parameters need not be displayed at all.

It is also possible to enter into the apparatus in advance the distance to be covered, as well as the desired time to cover the distance. The apparatus will then calculated the average speed to be run and will display this on the LCD 14. An alarm beep will be sounded using a piezo sounder 24 if the user is below or above the average speed, or a speed band around the required speed. In addition, if the user is running faster or slower than the target pace, the device will recalculate the required speed and use this to assist the runner to achieve the desired time.

The apparatus has the following buttons 56 to allow a user to input commands:

On/off Used to switch the device on and off. Start/Stop This starts and stops an active cycle. When this is pressed while in an active cycle it stores a marker which can subsequently be used for split times, or simply to indicate the reaching of a specific point such as the top of a hill. Pressing this button as well as the Set button at the same time will clear the device.

Set Sets a selection, such as:

set metric or imperial modes; set time of day and clock entries; set distance and expected time to complete

(goal); start uploading; calibrate the zero distance between feet when using the second embodiment of the invention

(which will be described below);

Mode Selects an operation mode, such as:

Select Time, Active, Reporting or Set-up mode. While in Active mode, the display will show Time to Expected Finish, Time per km/mile, Slowest/Fastest Km/mile, Time/Distance Above/Below Target to Meet Desired Completion Time etc. While in Set-Up mode the button will select modes such as: Set Up Time and Date, Select Metric or Imperial, Set Up Desired Time to Complete a Specified Distance etc. The user is also able to download data to a personal computer. Here, speed and optionally heart rate and/or altitude are averaged and stored at preset intervals, typically every 5 seconds, in a 64kbit serially interfaced EEPROM 16. This EEPROM 16 allows multiple read, write and erase cycles. To download the data to a personal computer, the apparatus includes a PC interface 28 which generates an infra red remote carrier output signal from the MC68HC05L25 microprocessor. This achieves contactless interfacing with the personal computer. The stored speed, distance, heart rate and other data are transmitted via a buffer B3, which drives an infra red diode 26, typically an Optek OP293B device. This is a very short range transmitter, and will rely on the receiver being within a range of up to 10 cm from the main unit, with clear line of sight between the two devices. Correct receipt of data is signaled via the low frequency receiver 18, normally used for heart rate data reception.

In a second embodiment of the invention, apparatus is used to measure the flight time of radio frequency signals transmitted between the user's feet. This is in turn used to more accurately measure the speed of and distance travelled by the user. Here, speed of movement is determined by measuring the continuous variations of the distance between the feet, including the actual step length which is the maximum distance between the feet. This is done using ranging time-of-flight measurements between the feet using a radio frequency transponder attached to each foot. Each transponder transmits an encoded packet or burst of a number of cycles at a predetermined frequency when it has received a similar burst from the other transponder. The time to transmit and receive a predetermined number of packets will incorporate the flight time ofthe radio frequency signals, which is proportional to the distance or range between the transponders. The second embodiment of the invention is illustrated in Figures 2 to 6. Referring first to Figure 2, this part of the apparatus is similar to the apparatus of Figure 1 described above and like parts are denoted by like reference numerals. However, in this embodiment the GPS receiver is replaced by a 125kHz receiver 30. The receiver 30 receives a serially encoded 10 bit data stream indicating the distance between steps from transponders 32 and 34 (which will be described in detail below). The signal is amplified by an operational amplifier B6, and applied to the EVI input on the microprocessor 8. The microprocessor contains an integral frequency measurement counter, which acts as an event counter. It therefore allows the microprocessor to easily demodulate the received frequency, thereby allowing the microprocessor to receive the serial 10 bit data string. The microprocessor will use the information pertaining to the distance between the feet to calculate speed by integrating the distance between the feet over time. Using the actual step length the microprocessor can also calculate the distance travelled.

The two nearly identical battery operated transponders 32 and 34 are attached to each foot. The devices are small and light enough to be attached to shoes by being laced to the top of the shoes with normal shoelaces, as illustrated in Figure 6. Before the user sets out, he/she will have to calibrate the transponders, typically by standing against a straight object with the backs of both of his feet against the object. The Set button on the microprocessor 8 is then pressed while not moving. This calibrates the unit when effectively zero distance exists between the feet.

The radio frequency time of flight measurement is implemented using digital techniques to allow for easy integration into digital, application specific, integrated circuits. This allows the transponders to be small enough to fit on a user's feet while still being cost effective.

Referring to Figure 3, the overall interaction ofthe system can be seen. The transponders communicate with each other and one of the transponders also contains circuitry for measuring a transmission cycle and transmitting data to the main unit apparatus described above. Figures 4 and 5 detail in block schematic form the circuitry of the transponders and the frequency measurement and transmit circuitry respectively.

The transponders 32 and 34 measure distance using a low power 13.5 MHz RF carrier. This frequency was selected as it is in an unlicensed band, used mostly for RF identification. Bursts or packets of 16 cycles are transmitted by one transponder at a time, whereupon the transponder will wait to receive 16 cycles from the other transponder. The second transponder listens for 16 carrier cycles, and then goes into transmit mode once it has received these. In transmit mode, it transmits 16 cycles.

To avoid lock-up, one transponder will start transmitting if it does not detect any signal and the other will be forced into receive mode if it does not detect any signal. The period of a full cycle will be the time taken for two bursts of 16 cycles, each burst being 1.186 microseconds, of 13.5mHz to be transmitted, plus the time of flight. The time of flight will be basically the distance between the feet divided by the speed of light, which is approximately 0.033333 nanoseconds per centimeter. The circuitry required to measure this very short time delay is too complicated for consumer applications. However, this difficulty is overcome by transmitting a large number of cycles, being 8192 cycles in this case, which will effectively multiply the time delay per centimeter by 8192 times two, resulting in 546 nanoseconds per centimeter, which is measurable using relatively low speed integrated circuits.

Each transponder contains nearly identical circuitry which is illustrated in Figure 4. This circuitry is integrated into the general transponder integrated circuit. The only difference between the transponders is in the external strapping of the carrier detect input pin 36, which forces one transponder to transmit if no signal is present, and the other to receive when no signal is present. A crystal controlled oscillator 38 operating at 13.5MHz can be started and stopped in a known state with the oscillator input being grounded via a mosfet 40. A simple linearly based high gain inverter 42 is used as the oscillator. In transmit mode, a first flip-flop 44 is reset, with its output Q being low. This allows the oscillator 38 to operate, and enables a first counter 46. A transmit buffer 48 is also enabled. When the first counter's output Q5 goes high, it indicates that 16 cycles at 13.5 MHz have been transmitted, and it then sets the flip-flop 44, which in turn stops the oscillator with its output still in the high state. It also resets the counter 46, which in turn causes Q 5 to go low again.

When the output Q of the flip-flop 44 is low, a receiver counter 50 is enabled, and the transmitter buffer 48 is fully disabled. At this point the receiver waits for 16 cycles at 13.5 MHz to be received from the other transponder. The receiver counter 50 counts the received clocks, and when it has received 16 cycles, it resets the flip-flop 44, causing its output Q to go low, which again initiates the transmit mode. The carrier detect circuit 36 detects if any carrier from either transponder is present. If not, the output of the carrier detect circuit 36 goes high, thereby resetting the flip-flop 44, and forcing a transmit cycle. A delay of approximately 1 millisecond caused by the resistor and capacitor time constant at the input of the carrier detect circuit ensures that it will not force a transmit mode until well after the other transponder should have transmitted. The input to a second carrier detect circuit 52 is permanently strapped high to disable it in the one transponder, while in the other transponder it is connected to the external signal detection components to provide carrier detection, which will force this transponder into receive mode if no signal is received. The "Cycle Completed" output pin 54 toggles repetitively at the rate of completion of each transmit burst and receive burst cycle. This is used in the one transponder for determining the period, hence the distance, and is not used in the other transponder. This frequency will vary from nominally 0.42187 MHz at 0cm distance to 0.42069 MHz at 1 meter distance.

The integrated circuit illustrated in Figure 5 multiplies the number of transmit/receive cycle periods by 8192, to measure the frequency of the signal, and to extract this value from the zero distance value in order to provide a 10 bit value directly related to the distance between the feet. It also provides the frequency-shifted 125kHz transmit signal to serially transmit the distance signal to the main device.

A first counter 74 is a 14 bit down counter clocked by the Cycle Completed signal. The period of Q14 is measured, since this reflects the period of the cycles multiplied by 8192. A second counter 58 is an 18 bit counter, and is clocked by a fixed 10MHz crystal controlled clock 66. It counts up when its clear signal is low, and when the output Q of a flip-flop 60 is low. It will count up to between 194180 for 0cm distance and 194726 for lm distance. The 18 bit subtractor logic block 62 subtracts the value of 194180 to provide a 10 bit value ranging from 0 to 546 for lm. This means that a resolution of approximately 2mm is achieved, as the count for 1cm will be 5. When Q14 on the counter 74 goes high, it clocks the output Q of the flip-flop 60 high, which stops the frequency measurement cycle, and starts a serial transmit cycle.

The serial transmit cycle allows the transmission of the 10 bit data. A third counter 64 is clocked by the 10 MHz clock 66, and is a 7 bit programmable divider, able to divide either by 77 for an output frequency of 128.87 kHz, or by 83 for an output frequency of 120.481 kHz. This counter 64, as well as counters 68 and 70, are enabled by the output Q of the flip-flop 60 being high. The counter 70 divides the output clock from the counter 64 by 32 in order to allow for 32 120/129 kHz cycles per bit. The serial bit count is determined by the counter 68.

A 16 to 1 line multiplexer 72, with its select address determined by the counter 68, is used to output the relevant data bit. Its input 2 is grounded to indicate a start bit, and its inputs 3 to 12 are connected to the 10 bits indicating the distance. Its input 13 is grounded to indicate a start bit. When the counter 68 reaches the count of 15, it resets the counter 58 to zero, and causes the flip-flop 60 to reset, resulting in its Q output going low, thereby resetting and disabling the counters 64, 68 and 70. The counters 74 and 58 start counting from zero again, thereby repeating the measurement cycle.

In both embodiments the main unit is a compact battery operated unit, which was clipped onto the waist of the user in a variety of manners as is illustrated in Figure 7. It can either be clipped onto the belt, or onto the waist strap of the user's shorts. The LCD display 14 is at the top of the device allowing the user to observe the speed and optionally the distance or time readings. The buttons 56 are also at the top of the unit, allowing the user to access them easily.

Claims

CLAIMS:

1. Apparatus for determining the speed of travel and the distance travelled by a user comprising:

2. Apparatus according to claim 1 wherein the sensor is a shock sensor arranged to detect each step ofthe user.

3. Apparatus according to claim 1 or claim 2 wherein the apparatus includes a display for displaying parameters to the user including at least one ofthe user's speed, distance travelled since a start time and time elapsed since a start time.

4. Apparatus according to any one of claims 1 to 3 wherein the processor means is a microprocessor and including input means arranged to allow a user to input commands to the microprocessor.

5. Apparatus according to any one of claims 1 to 4 including a sounding device operable by the microprocessor when the user is travelling at a speed above or below a predetermined speed range.

6. Apparatus according to any one of claims 1 to 5 including an altitude sensor.

7. Apparatus according to any one of claims 1 to 6 including communication means for communicating with a heart rate monitor.

8. Apparatus according to any one of claims 1 to 7 including a memory device for storing data relating to predetermined user defined parameters and a communication device for downloading the stored data to an external device.

9. Apparatus according to claim 8 wherein the data is the user's speed, the user's heart rate, the altitude and/or the distance travelled by the user.

10. Apparatus for determining the speed of travel and the distance travelled by a user comprising:

a first transmitter connectable to a first limb of the user, the first transmitter being adapted to transmit a plurality of signals; a second receiver connectable to a second limb of the user, the second receiver being adapted to receive the plurality of signals transmitted from the first transmitter; and

processor means connectable to the receiver, wherein the processor means in arranged to calculate the time taken for the plurality of signals to travel from the first transmitter to the second receiver to calculate the distance between the first transmitter and the second receiver and thereby determine the speed of travel and the distance travelled by the user.

11. Apparatus according to claim 10 wherein the processor means is arranged to measure differences in the time taken for the plurality of signals transmitted by the first transmitter to be received by the second receiver due to changes in the distance therebetween.

12. Apparatus according to claim 10 or claim 11 wherein the first transmitter includes an associated first receiver and the second receiver includes an associated second transmitter.

13. Apparatus according to claim 12 wherein the first transmitter and first receiver comprise a first transponder and the second transmitter and second receiver comprise a second transponder.

14. Apparatus according to any one of claims 10 to 13 including a sensor for detecting movement ofthe user.

15. Apparatus according to claim 15 wherein the sensor is a shock sensor.