Automatic velocity control treadmill using pressure sensor array and fuzzy-logic

The present invention relates to an automatic speed-controlled treadmill that uses a pressure sensor array and a method of operating the same, and has a technical feature such that it detects the load of an exerciser, calculates variation in pace speed and an exercise center, and then automatically controls the driving speed of a walking belt.

In general, a treadmill is exercise equipment that enables running or walking exercise to be performed indoors. As shown in FIG. 1(a), the treadmill includes a walking belt 12, a driving device for moving the walking belt 12, and control means for controlling the driving device. The driving device includes a plurality of rollers for supporting the walking belt 12 and a motor for driving the rollers. The control means controls the driving device in association with the motor. According to such a typical treadmill, a user moves the walking belt 12 by driving the motor through an input module 11, and an exerciser steps on the walking belt 12 and walks or runs at the driving speed of the walking belt 12, thereby achieving exercise effects.

Therefore, in order to obtain appropriate exercise effects, the exerciser must run at the speed of rotation of the walking belt 12. When it is desired to change the rate of exercise, the exerciser must control the rotating speed by manipulating the button, knob, or the like of the input module 11 of the treadmill and then run in conformity with the rotating speed of the walking belt 12. That is, in order for the exerciser to change the running speed as desired while running, the exerciser must manually manipulate a speed change button or the like, which is located in the input module 11 of the treadmill.

However, in the case where the exerciser manually manipulates the speed of the treadmill using buttons during running exercise, there is inconvenience in manipulation. In particular, for the elderly, the weak and children, who have difficulty in maintaining their balance, and patients, who require rehabilitation, there is the concern that they may fall down due to the changed speed of the walking belt 12 after the change of the speed.

To solve this problem, there is a method of detecting the position of an exerciser by radiating ultrasonic waves toward the exerciser and calculating the arrival time of an ultrasonic wave reflected from the exerciser, and increasing or decreasing the rotating speed of a walking belt based on the detected position. However, this apparatus has many limitations to application to practical products in that reflectivity varies with the dress or movement of the body of an exerciser, which is the ultrasonic reflector, so that it is difficult to measure the position of the exerciser and a measured a signal is disturbed, with the result that there are many limitations in the application thereof to practical products.

To overcome the limitations, an invention (Korean Unexamined Patent Publication No. 10-2002-0013649), entitled “Treadmill Capable of Detecting Position of Exerciser and Speed/Position-Adaptive Control Method for the Treadmill,” which controls speed using optical sensors, rather than ultrasonic waves, has been proposed. That is, an apparatus that detects the exercise position of an exerciser using optical sensors 15a and 15b, including light-emitting units 15a on one of two opposite sides of a walking belt and light-receiving units 15b on the other side thereof, and controls the speed of the walking belt, has been proposed, as shown in FIG. 1(b). In other words, the apparatus detects the position of an optical sensor, which is turned off by the leg of an exerciser who runs on the walking belt, increases the speed of the walking belt if the exerciser is positioned before the immediately previous position, and decreases the speed of the walking belt if the exerciser is positioned after the immediately previous position. However, the method of controlling the position of a walking belt using optical sensors has a problem in that speed is inaccurately controlled because only the position of a user\'s foot is detected using an optical sensor, regardless of whether it is the right or left foot, and then the speed is controlled. Furthermore, the apparatus has a problem in that the position of a user\'s foot is not accurately detected when light radiated from the light-emitting units is weak due to a problem, such as an excessive distance between the light-emitting units 15a and the light-receiving units 15b because the light-emitting units 15a and the light-receiving units 15b are disposed on either the left or right sides of the walking belt.

Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to automatically control the speed of a walking belt in conformity with an exerciser\'s rate of exercise without requiring an exerciser to manually control the rate.

Another object of the present invention is to provide a scheme for controlling the speed of a walking belt without using the conventional ultrasonic waves and optical sensors.

In order to accomplish the above objects, an automatic speed-controlled treadmill of the present invention an automatic speed-controlled treadmill using a pressure sensor array, including a walking belt disposed on the bottom of the treadmill and configured to function as a pace surface of an exerciser; a pressure sensor array including pressure sensors for detecting loads of the exerciser\'s feet and outputting the detected loads of the feet as load detection signals, the pressure sensors being disposed in a plurality of arrangements between the bottom of the treadmill and the walking belt; a pace speed status storage unit for storing a pace speed and variation in pace speed of the exerciser who takes exercise on the walking belt; and a control unit provided with an algorithm for receiving the load detection signals from the pressure sensors and then calculating a pace speed of the exerciser, calculating a difference between a previous pace speed and a current pace speed as the variation in pace speed, calculating the exercise center of the exerciser from unique position values of the pressure sensors, and proportionally accelerating/decelerating a driving speed of the walking belt in consideration of the variation in pace speed and the exercise center.

In addition, the present invention provides an automatic speed-controlled treadmill using a pressure sensor array, including a walking belt disposed on a bottom of a treadmill and configured to function as a pace surface of an exerciser; a pressure sensor array comprising pressure sensors for detecting loads of the exerciser\'s feet and outputting the detected loads of the feet as load detection signals, the pressure sensors being disposed in a plurality of arrangements between the bottom of the treadmill and the walking belt; a pace speed status storage unit for storing a pace speed and variation in pace speed of the exerciser who takes exercise on the walking belt; and a control unit provided with an algorithm for receiving the load detection signals from the pressure sensors and then calculating the pace speed of the exerciser, calculating a difference between a previous pace speed and a current pace speed as the variation in pace speed, calculating an exercise center of the exerciser from unique position values of the pressure sensors, and proportionally accelerating/decelerating the driving speed of the walking belt based on a fuzzy theory using a fuzzifier, a rule base, a fuzzy inference engine, and a defuzzifier.

The pressure sensor array includes a right pressure sensor array provided on a right side of a longitudinal center line of the walking belt and configured to detect a load of a right foot of the exerciser; and a left pressure sensor array provided on a left side of the longitudinal center line of the walking belt and configured to detect a load of a left foot of the exerciser.

The pressure sensors have respective unique position values indicating positions thereof. The pace speed is obtained by dividing a pace distance, indicating a distance between paces of the exerciser, by a pace time period, indicating a time period of inter-pace movement of the exerciser (the pace=the pace distance/the pace time period).

Assuming that ‘an average lifting position=(a right foot lifting position+a left foot lifting position)/2’ and ‘an average stepping position=(a right foot stepping position+a left foot stepping position)/2’, the pace distance is obtained by ‘the pace distance=the average stepping position−the average lifting position’.

Assuming that ‘an average lifting time point=(a right foot lifting time point+a left foot lifting time point)/2’ and ‘an average stepping time point=(a right foot stepping time point+a left foot stepping time point)/2’, the pace time period is obtained by ‘the pace time period=an average stepping time point−an average lifting time point’.

Assuming that ‘an average lifting position=(a right foot lifting position+a left foot lifting position)/2’ and ‘the average stepping position=(a right foot stepping position+a left foot stepping position)/2’, the exercise center is obtained by ‘the exercise center=(the average stepping position+the average lifting position)/2’.

The control unit accelerates the driving speed of the walking belt in steps as the variation in pace speed becomes higher and the exercise center becomes closer to a front portion of the walking belt, and decelerates the driving speed of the walking belt in steps as the variation in pace speed becomes lower and the exercise center becomes closer to a rear portion of the walking belt.

In addition, the present invention provides a method of controlling a driving speed of a treadmill using a pressure sensor array, the method including a first step of driving a walking belt of a treadmill through input manipulation of an exerciser; a second step of receiving load detection signals from pressure sensors for a first block, with a foot pace, including four positions (a left foot stepping position, a right foot stepping position, a left foot lifting position, and a left foot stepping position), being set to each block; a third step of, for the first block, calculating a pace speed of the exerciser using the load detection signals, calculating a difference between a previous pace speed and a current pace speed as variation in pace speed, and calculating an exercise center using unique position values of the pressure sensors; a fourth step of proportionally accelerating/decelerating the driving speed of the walking belt in consideration of the calculated variation in pace speed and the calculated exercise center; and a fifth step of receiving the load detection signals from the pressure sensors for a next block until the walking belt is stopped, and repeating the third step and the fourth step.