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ADVANCED AUTOMATED DEVICE CONTROLLER FOR KNEE REHABILITATION AND RECOVERY
[1]
M.Srinivasaperumal,
[2]S. Karthikeyan ,
[3]N.Rushmi priya,
[4]P.Kokila
[1, 2, 3, 4]
Dept. of ECE, SNS College of Technology, Coimbatore, India
ABSTRACT:
Continuous Passive Motion (CPM) device is frequently used for knee rehabilitation to improve the range of motion or enlargement of the knee following injuries or surgeries. The main aim is to the advanced Knee Rehabilitation using Touch Screen Automated Device Controller. The device is capable of bending or elongating the knee joint in the range of motion from 0 degrees to 120 degrees with the speed of 30 degrees/minute to 150 degrees/minute. The device consists of a touch screen or LCD display, a microcontroller, a motor driver, a DC motor, an encoder, two safety sensors, an original point sensor and a mechanical part.
The advanced automated CPM device gives better benefits and it is a portable size with a smooth motion of the motor system. With the advantages of a touch screen automated device controller provides a user friendly interface for the controller.
Key words: Continuous Passive Motion, Rehabilitation, Knee Joint Stiffness, Touch Screen, Micro Controller, Motor.
1. INTRODUCTION
There are a lot of joints in our human body and uses many degrees of freedom of joints in action for daily life and operation. Therefore deduction of the degrees of freedom will decrease the standard of life. Muscle weaknesses due to old ages, queue and human resources accidents are the main reasons for human motion defect. To improve the capability of motion, the defect muscles could be strengthened by using rehabilitation treatment. Normally human being are having problems in forelimb or leg fluctuation so we go for physiotherapist and involves a series of repeated and physical action for several days or several weeks. Touch Screen Automated Device Controller is the advanced CPM device. The CPM Device replace the duty of the physiotherapist and realize the physical motion without the guidance of a physiotherapist. Continuous Passive Motion (CPM) device is mostly used for knee rehabilitation by helping the joints move gradually in order to improve the range of motion (ROM) or enlargement of the knee following injuries or surgeries.
In addition, the application of CPM is to reduce post-operative pain, decrease the number of adhesions, decrease the amount of atrophy experienced by the surrounding and supporting muscle, promote the speed of recovery, improve the range of motion in a much shorter time, and reduces the risk of deep vein thrombosis and post traumatic osteopenia . The concept of a therapeutic use of CPM device has been widely testing during the past
131 | P a g e few period as verification by a number of devices that are apply continuous passive motion on the leg and joint of a patient for such purpose.
However, most of them have the following disadvantages: they are generally heavy and bulky; they are not able to give smooth motor movement; they cannot offer the same anatomical adjustability; and they do provide a user friendly interface for the controller.
In view of the above, it is clear that there is a well defined need for a CPM device. Consequently, this paper describes Knee Rehabilitation Using Touch Screen Automated Device Controller which is able to eliminate the above mentioned disadvantages by proposing a CPM device that offers a portable size with a smooth motion of the motor system. It is also readily adaptable to either a right or left limb, and can be easily adjusted to accommodate legs of different lengths. Also, with the advantages of a touch screen based controller the advanced CPM device provides fast access with different features to input the patient data, can effectively increase operator accuracy, reduces training time, and improves overall operational efficiencies.
2. STATEMENT OF THE CONTRIBUTION
The schematic diagram of the advanced CPM device as shown in Fig.1 and the device consists of the following part.
Figure 1. Schematic diagram of the developed CPM device.
A. TOUCH SCREEN OR LCD DISPLAY
A 3.2 inch touch screen or LCD display was used to enter all specification data such as starting knee-angle, ending knee-angle, speed and operating time. The data will be carried to a microcontroller and produce the control signals to drive the motor. In the main menu there are 3 modes they are Auto Run, Manual and Setting Modes to operate the advanced device as shown in Fig.2.
Figure 2. The main menu selection on the touch screen LCD display.
132 | P a g e The manual mode is shown in Fig.3. The manual mode is the first mode used to find the patient optimal values of the knee elongating angle, knee bending angle and speed. The range of the motion speed can be modified from 30 degrees/minute to 150 degrees/minute with 0 to 100 levels and the degree of motion is from 0 degrees to 120 degrees.
Figure 3. The touch screen LCD display of the manual mode.
The increment of the motion degree can be done easily by simply pressed the flexion (bending) and the degree of motion is decreased by pressed the extension (elongating). The patient optimal values are obtained and the data will be entered in the setting mode as shown in Fig.4 and then stored in the memory.
Figure 4. The touch screen LCD display of the setting mode.
Auto run mode as shown in Fig.5. Auto run mode presents the stored data from the setting mode to reconfirm the values of the data before starting the procedure.
Figure 5. The touch screen LCD display of the auto run mode before starting the operation & Current status of the device .
133 | P a g e The range of motion (ROM), duration time and speed are clearly apparent to both the operator (therapist) and the patient. The current status of the device on touch screen automated device or LCD display as shown in Fig.5 and the device starts operating. The device can be paused or stopped anytime if the patient feels uncomfortable.
B. MICROCONTROLLER
An ET ARM7-LPC2138 from Philips was employed as a microcontroller. The signals from touch screen automated device, encoder, safety sensor and original point sensor are input to the microcontroller to control the motion of the motor either in a clockwise or anti clockwise direction to move to the desired position. The speed data are entered on the touch screen automated device and sent to the microcontroller to generate signals using Pulse Width Modulation (PWM) technique to move the motor at the required speed.
C. MOTOR DRIVER
The drive system of the advanced CPM device is based on the double full bridge driver, L298N. The signals produced from the microcontroller are sent to the IC L298N to control the direction and speed of the motor.
D. MOTOR
A gear reducer is mounted to a 12V DC motor to increase the torque and decrease the maximum speed of the motor of about 110 rpm. The maximum axial load of the motor with gear is approximately 400 N. The motor output will provide a smooth motion and to maintain mechanization that is always adequate for the mass of the limb to be moved. Two limit switches are used as safety sensors to assure the range of motion as shown in Fig.6.
The mechanical part of the CPM device reaches the safety sensors and the contact switch will be activated and the microcontroller will stop the motion.
Figure 6. Structure diagram of the developed CPM device.
E. ENCODER
A rotary encoder model E6B2-CWZ6C from OMRON is used for a knee-angle sensor to track the degree position of the motor shaft and the direction of rotation. This encoder is simply built into a hinge of the CPM’s mechanical linkage as shown in Fig.5 such that the output signal from the rotary encoder varies as the knee-
134 | P a g e angle varies. The output signal from the encoder will be further processed at the microcontroller and the current degree position is displayed on the screen as shown in Fig.4.
F. SAFETY SENSOR
Two limit switches are used as safety sensors to ensure the range of motion as shown in Fig.7.When the mechanical part of CPM device reaches the safety sensors, the contact switch will be activated and the microcontroller will stop the movement of the motor.
G .ORIGINAL POINT SENSOR
An Original Point Sensor as shown in fig.5. is a limit switch that indicates the original position and is typically at 0 degree. Every time when the CPM device is started the mechanical part will move until it contacts the original point sensor and results in the original position.
H. MECHANICAL PART
The design of the advanced CPM device is based on the slider-crank mechanism as shown in Figure7. The upper leg length (point2) and lower leg length (point 3) are calculated from the height of the patient by the following equation:
Upper leg or lower leg length = [(h/2)-a]/2
where h is the height of the patient and a is the height from floor to the ankle (it is normally equal to 6 cm) The lengths of the upper leg (point 2) and lower leg (point 3) need to be evaluated because the combination of these lengths represent the ball screw length, the distance between point 1 and point 4 as shown in Fig.8.
Figure 7. Slider-crank mechanism used to design the CPM device.
3. RESULTS
We design a touch screen automated device based on CPM for the knee rehabilitation is advanced as shown in Fig.10 & 11. The device execute the flexion (bending)-extension (enlarging)movement in the range of motion from 0 degrees to 120 degrees with the speed of 30 degrees/minute to 150 degrees/minute. The knee-angle, speed and operating time can be modified and displayed on the 3.2 inch touch screen automated device or LCD display.
135 | P a g e Figure 9. 3D structure design, working, Photograp of the developed CPM device.
The system specifications are presented on Table 1.The CPM was modified here to offer a wide range of settings for patients ranging in height between 130 cm and 190 cm. The lengths of the upper leg and lower leg can be modified from 29.5 cm to 44.5 cm to suit the size of the patient.
The torque want to drive the CPM device is also calculated. After the optimal lengths of the upper leg part, lower leg part and ball screw are applied to the CPM device is designed in 3D with the Solid Works software as presented as shown in Fig.9. The dimensions of the device are 110 cm Length, 34cm Width and 45cm Height.
4. CONCLUSION
The Touch Screen Automated Device Controller and it advanced CPM device gives better results and it offers a portable size with a smooth motion of the motor system. It is design in such a way that it can rehabilitate both left and right knees and it can be easily modified to accommodate for different limb dimensions. The manipulator can perform the flexion (bending)-extension (enlarging) motions for the knee rehabilitation. The advantages of a touch screen automated device based on the controller of the CPM provides fast access with different features to input the patient data can effectively increase operator accuracy, reduces training time, and improves overall operational efficiencies. The next step for this research is for clinical evaluation of the device with rehabilitation professionals.
Table 1 System Specifications
S.No. Specification
1
Microcontroller, ET-ARM7 STAMP LPC2138
16/32-Bit MCU ARM7TDMI-S No.LPC2138 from Philips
+3.3V Power Supply only (3.0V-3.6V±10%Error)
512 KB Flash Memory in MCU and 32 KB Static Ram 2
Motor driver, No.L298N, will give power to DC motor in accordance with programme pulse signals to control direction and speed.
3 DC Motor with gear reducer, 12 V, 110 RPM.
4 Operational Voltage: 220 V, 50 Hz
136 | P a g e 5 Display Module 3.2 inch TFT LCD Colour + Touch Screen with 240x320 Pixel.
6 Display Module 3.2 inch TFT LCD Colour + Touch Screen with 240x320 Pixel.
7 Leg Support is made of stainless steel.
8 The operating time can be adjusted in hour and minute units.
9 Dimensions: 110 cm L x 34 cm W x 45 cm H.
10 Weight: 10 kg.
11 Speed: 30° - 150°/minute with 0 –100 levels.
12 Range of Motion: Extension (0°) to Full Knee Flexion(120°)
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