US20080182727A1

US20080182727A1 - Method of controlling motor for driving treadmill belt

Info

Publication number: US20080182727A1
Application number: US11/764,570
Authority: US
Inventors: Chii-Maw Uang
Original assignee: Uei Sun Tech Co Ltd
Current assignee: Uei Sun Tech Co Ltd
Priority date: 2007-01-26
Filing date: 2007-06-18
Publication date: 2008-07-31
Also published as: TW200832886A

Abstract

A method of controlling a motor for driving a treadmill belt includes the steps of a) providing a micro controller unit having a proportional integral derivative controller and a load predictor; b) providing a driver controllable by the micro controller unit to drive the motor used for driving the treadmill belt; c) detecting a load and a speed of the motor and sending a load feedback signal and a speed feedback signal corresponding to the detections to the micro controller unit by a load meter and a speed meter respectively; d) running a procedure and outputting a control signal to the driver by means of computation of the proportional integral derivative controller and the load predictor; e) regulating the output status of the motor by the driver subject to the control signal received; and f) repeating step c) to step e) till end of the procedure.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates generally to a method for controlling a treadmill and more specifically, to a method of controlling a motor that is used for driving a treadmill belt.
2. Description of the Related Art
A treadmill is a piece of indoors sporting equipment used to allow for the motions of running or walking without traveling any distance outdoors. Basically, a motor-driven treadmill comprises an endless belt on which the user runs or walks, and a motor for driving the endless belt.
The treadmill belt drive motor of a conventional treadmill can be an induction motor, AC motor, or DC motor. When running at a high speed, the treadmill belt drive motor of a conventional treadmill provides a high horsepower. The design of a conventional treadmill is based on the concept that the load from the user is assumed to be linear so that the treadmill belt drive motor drives the treadmill belt at a constant power. However, in actual practice, the load from the user is nonlinear. Every step from the user adds a load to the motor instantaneously. Because the treadmill belt drive motor of a conventional treadmill provides a constant output, the output of the treadmill belt drive motor becomes insufficient during the instant in which the load is changed, causing a sudden speed reduction or cogging of the treadmill, as shown in FIG. 1, and the user will feel unstable. Increasing the power of the treadmill belt drive motor can eliminate the sudden speed reduction or cogging problem. However, when the load from the user is reduced (for example, the user's step becomes light), the power of the treadmill belt drive motor becomes excessively high, and the user may slip and fall. In another word, a conventional treadmill belt drive motor has the drawback of difficult speed change control. High power consumption and high noise level are also the drawbacks of conventional treadmill belt drive motors. Further, increasing the output of the conventional treadmill belt drive motor of a treadmill will relatively increase the power consumption and electricity expense. Therefore, this is not an economic way. Further, the noises produced during operation of the treadmill belt drive motor of a conventional treadmill may bother the user.
To improve the aforesaid problems, an inverter may be installed to control the operation of the treadmill belt drive motor by means of open-loop control, allowing for speed change of the treadmill belt drive motor. However, an inverter for this purpose is expensive. The use of an inverter in a treadmill greatly increases the manufacturing cost. Further, when the frequency of the treadmill belt drive motor of a treadmill is converted to a low speed mode, the output torque of the treadmill belt drive motor is relatively reduced, and a speed reduction or cogging problem will occur at this time. Further, sound absorbing materials may be used in a treadmill and set around the treadmill belt drive motor to reduce the noise level. However, the installation of the sound absorbing materials affects heat dissipation of the treadmill belt drive motor. Accumulation of thermal energy may cause the treadmill belt drive motor to malfunction.
Therefore, it is desirable to provide a treadmill belt drive motor control method that eliminates the aforesaid problems.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances in view. It is one objective of the present invention to provide a method of controlling a motor that is used for driving a treadmill belt, which can adjust the power and speed of the motor subject to the load and make compensation to an instantaneous load, providing the advantages of frequency conversion control and good power stabilization.
To achieve this objective of the present invention, the method of controlling a motor used for driving a treadmill belt comprises the steps of a) providing a micro controller unit having a proportional integral derivative controller and a load predictor; b) providing a driver controllable by the micro controller unit to drive the motor used for driving the treadmill belt; c) detecting a load and a speed of the motor and sending a load feedback signal and a speed feedback signal corresponding to the detections to the micro controller unit by a load meter and a speed meter respectively; d) running a procedure by the micro controller unit and outputting a control signal to the driver by means of computation of the proportional integral derivative controller and the load predictor; e) regulating the output status of the motor by the driver subject to the control signal received; and f) repeating step c) to step e) by the micro controller unit and the driver till end of the procedure.
By means of the aforesaid method, the invention regulates the power and speed of the treadmill belt drive motor subject to the load, and makes compensation to instantaneous load. When compared to conventional treadmill designs, a treadmill constructed according to the present invention has the advantages of frequency conversion control and good power stabilization. By means of the use of a DC brushless motor to substitute for a conventional treadmill belt drive motor, the invention has the advantages of low power consumption, low noise level, and low manufacturing cost.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

BRIEF DESCRIPTION OF THE DRAWING

The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a plot showing the relationships between user's steps and forces of motor, load and treadmill belt according to the prior art;

FIG. 2 is a flow chart of the method of controlling a motor that is use for driving a treadmill belt according to a preferred embodiment of the present invention;

FIG. 3 is a system block diagram of the preferred embodiment of the present invention;

FIG. 4 is a control block diagram of the preferred embodiment of the present invention;

FIG. 5 is a flow chart showing the operation of the micro controller unit (MCU) according to the preferred embodiment of the present invention; and

FIG. 6 is a plot showing the relationships between user's steps and forces of motor, load and treadmill belt according to according to the preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIGS. 2-6, a method of controlling a motor for driving a treadmill belt in accordance with a preferred embodiment of the present invention includes the following steps.
a) Provide a micro controller unit (MCU) 10, which includes a controller unit (CU) 11, an arithmetic logic unit (ALU) 12, a timer 13, a proportional integral derivative (PID) controller 14, a load predictor 15, and a plurality of input/output (I/O) ports 16. The CU (controller unit) 11 enables the MCU (micro controller unit) 10 to run control functions. The ALU (arithmetic logic unit) 12 enables the MCU (micro controller unit) 10 to run a logic algorithm function and an arithmetic algorithm function. The timer 13 enables the MCU (micro controller unit) 10 to run a time sequence control function. The PID controller (proportional integral derivative controller) 14 enables the MCU (micro controller unit) 10 to run a compensation algorithm on feedback signal for estimating the speed of the treadmill. The load predictor 15 enables the MCU (micro controller unit) 10 to run a compensation algorithm on feedback signal for estimating the user's step load. The I/O ports (input/output ports) 16 allow connection of other external devices to the MCU (micro controller unit) 10. When the treadmill is started, the MCU (micro controller unit) 10 will start first an initialization procedure and offer a power compensation of a predetermined value to the motor 30.
b) Provide a driver 20 and a motor 30, wherein the driver 20 is electrically connected to one I/O port 16 of the MCU 10 and controllable by the MCU 10; the motor 30 is electrically connected to the driver 20 and drivable to run by the driver 20. The motor 30 is selected from DC motor or brushless motor, preferably DC brushless motor. The motor 30 according to this embodiment is a DC brushless motor;
c) Use a load meter 40 and a speed meter 50, which are respectively electrically connected to the I/O ports 16 of the MCU 10, to detect the load of the motor 30 and the revolving speed of the motor 30 and continuously send out a load feedback signal 42, which indicates the status of the load by current value, and a speed feedback signal 52.
d) After receipt of the load feedback signal 42 from the load meter 40 and the speed feedback signal 52 from the speed meter 50, the MCU 10 runs subject to a procedure 60 and computes by means of the PID controller 14 and the load predictor 15, and then outputs a control signal 17, wherein the procedure 60 includes the following steps.

- d1) Use the MCU 10 to record the load feedback signal 42 from the load meter 40 and the speed feedback signal 52 from the speed meter 50, thereby knowing the operation status of the motor 30 at the first footstep and the second footstep.
- d2) When the motor 30 continuously runs and a predetermined number of footsteps is reached, the MCU 10 compares the recorded data, and computes by means of the PID controller 14 and the load predictor 15 subject to a load prediction compensation algorithm 62 to obtain a computation result 18, which is the estimated output status of the motor 30 at the third footstep; wherein the predetermined number of footsteps according to this embodiment is 2.
- d3) The MCU 10 resets the content of the control signal 17 subject to the computation result 18 for regulating the output status of the motor 30 at the third footstep.

e) The driver 20 regulates the output status of the motor 30 upon receipt of the control signal 17;
f) The MCU 10 and the driver 20 repeat the step c) and step e) till end of the procedure 60 subject to that three footsteps are grouped as one unit to perform one execution loop.
When the user starts to use the treadmill, the MCU (micro controller unit) 10 runs with close-loop control. By means of recording the load feedback signal 42 and the speed feedback signal 52, the MCU (micro controller unit) 10 acknowledges the compensation status of the compensation value relative to instantaneous load during the first footstep and second footstep of the user; by means of the computation of the PID controller (proportional integral derivative controller) 14, the computation result 18 is used by the load predictor 15 to modify the output speed of the motor 30 at the third footstep; thus, the MCU (micro controller unit) 10 adjusts the compensation time to fit the user's footstep, and also adjusts the speed of the motor 30 and its power to reset the compensation value. In other words, the invention gives compensation to instantaneous load timely by means of real-time monitoring so that modification can be done properly subject to the exercise status of the user, assuring smooth running of the treadmill.
As stated above, the invention uses the programmable MCU (micro controller unit) 10 to control the operation of the motor 30 instead of an inverter. The MCU (micro controller unit) 10 has the advantages of frequency conversion control and good power stabilization. Further, the MCU (micro controller unit) 10 allows for internal optimal settings to fit different models. When compared to an inverter, the MCU (micro controller unit) 10 is relatively cheaper. Therefore, the invention can lower the cost of the treadmill. Further, because the motor 30 is a DC brushless motor, it has the advantages of low power consumption, low noise level, and low manufacturing cost. From the programmable point of view, the DC brushless motor 30 has a high speed change sensitivity and high power output. Therefore, the DC brushless motor 30 is suitable for digital control, and can achieve optimal control effects when used with the MCU (micro controller unit) 10. Further, the working temperature produced by the DC brushless motor 30 is relatively lower than a conventional motor. Relatively, the thermal energy accumulation problem is minor, preventing thermal damage to the components of the motor.
By means of the application of the aforesaid embodiment, the invention can adjust the power and speed of the treadmill belt drive motor subject to the load, and can make compensation to an instantaneous load. When compared to conventional designs, the invention smoothens the operation of the treadmill and has the advantages of frequency conversion control and good power stabilization. Further, the invention uses a DC brushless motor instead of a conventional treadmill belt drive motor, providing the advantages of low power consumption, low noise level, and low manufacturing cost.
The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.

Claims

1. A method of controlling a motor used for driving a treadmill belt, the method comprising the steps of:

a) providing a micro controller unit having a proportional integral derivative controller and a load predictor;

b) providing a driver controllable by the micro controller unit to drive the motor used for driving the treadmill belt;

c) detecting a load and a speed of the motor and sending a load feedback signal and a speed feedback signal corresponding to the detections to the micro controller unit by a load meter and a speed meter respectively;

d) running a procedure by the micro controller unit and outputting a control signal to the driver by means of computation of the proportional integral derivative controller and the load predictor;

e) regulating the output status of the motor by the driver subject to the control signal received; and

f) repeating step c) to step e) by the micro controller unit and the driver till end of the procedure.

2. The method as claimed in claim 1, wherein the micro controller unit provided in step a) comprises a controller unit, which enables the micro controller unit to run control functions.

3. The method as claimed in claim 1, wherein the micro controller unit provided in step a) comprises an arithmetic logic unit, which enables the micro controller unit to run a logic algorithm function and an arithmetic algorithm function.

4. The method as claimed in claim 1, wherein the micro controller unit provided in step a) comprises a timer, which enables the micro controller unit to run a time sequence control function.

5. The method as claimed in claim 1, wherein the micro controller unit provided in step a) comprises an input/output port, which allows connection of the driver.

6. The method as claimed in claim 1, wherein the micro controller unit provided in step a) comprises an input/output port, which allows connection of the load meter.

7. The method as claimed in claim 1, wherein the micro controller unit provided in step a) comprises an input/output port, which allows connection of the speed meter.

8. The method as claimed in claim 1, wherein the motor is selected from one of a DC motor and a brushless motor.

9. The method as claimed in claim 1, wherein the load feedback signal in step c) indicates the load status by a current value.

10. The method as claimed in claim 1, wherein the procedure in step d) includes the steps of:

d1) recording the load feedback signal and the speed feedback signal to obtain the operation status of the motor by the micro controller unit;

d2) comparing the recorded data by the micro controller unit when the footstep of a user running or walking on the treadmill belt reaches a predetermined number and obtaining a computation result from a computation using the proportional integral derivative controller and the load predictor according to a load prediction compensation algorithm; and

d3) resetting the control signal subject to the computation result for regulating the output status of the motor.