Based on the number of embedded processor implementation of traction therapy system (1)

0 introduction

Medicine for lumbar disc herniation, spinal disease usually isosceles take physical traction of conservative treatment.

This traction bed system is a two-stage platform for the treatment of the bed, with ARM, embedded processors and computers on the freedom of movement of the bed for distributed control and the implementation of external DC motor speed, slow traction and bed in any angle of fast spin for lumbar spine diseases physiotherapy.

1 system function and overall design

Traction bed with two-stage platform for the treatment of the bed.

Its bed body is divided into two periods before and after for a patient lying down. In the preceding paragraph has a fixed band the upper portion of the patient, using fixed lumbar traction belt and activities linked to the bedside. Traction motor is the direction of moving around. Bedside in the motor-driven to distraction from a certain distance forward, and the patient is the waist is fixed, so that the traction belt on spine will have a certain force. Bedside installation "S"-type traction tension sensor detection. The back of the bed will also be fixed with the lower part of the patient's waist to hip, fixed, and can be driven by the motor to the waist at the axis do horizontal plane swing, vertical axial tilt elevation rotation, and rotate to the left and right sides of a total of three degrees of rotation. The preceding bed of traction speed adjustable, rear section of the bed of the rotation angle and rotation speed can be set arbitrarily.

Traction bed for physicians provide four-degree adjustable physical movement, fully satisfy the physical treatment of lumbar spine disease.

Physical therapy, doctor according to patient's condition after the bed surface, the left and the right combination of slow distraction on the basis of the quick distraction for fair use to be able to play the role of "rectification".

The overall design of the traction bed take a distributed control system, as shown in Figure 1.

Computer as a host computer through RS-485 bus and three embedded controller (slave) distributed bus network on bed body motion control. Computer system operations control interface. System of complex control tasks are broken down into three parts, each consisting of three parallel real-time embedded controller executes. Among them, the traction motor and traction force of test and control consists of a complete SCM STC89C52RD +; three rotation angle detection and control of the company by Samsong 32-bit ARM RISC processor core; bed S3C44B0X processing all types on the limit switch and the switch quantity detection and output from another STC89C52RD + implementation.

Figure 1 system block diagram

2 system hardware design

2.1 STC89C52RD + based traction control

Speed traction therapy is DC motor driven head forward motion thus stretching fixed in patients with fixed belt waist, cushioned lumbar traction force exerted.

Traction force size and speed set by the doctor, and maintain for a period of time. Leave the duration can be combined with bed of rotation, and other actions for physical therapy.

Traction can be used by the bedside of S-type strain type tension sensor converts the analog signal.

The size and increase the incentive on the sensor size DC voltage. Sensor sensitivity for 2mV/V, DC excitation voltage is 5V, the sensor output maximum signal to 10mV. If the force sensor measuring range of 0-200Kg, the corresponding sensor output analog signal 0-10mV. The signal is amplified by the instrumentation amplifier AD623 500 times after 0-5V, via the "L"-shaped inductance, capacitance passive network filtering input to 10-bit A/D converter TLC1549. Traction force signal frequency is low, the processor per second sampling 20 times. Using a dedicated STC89C52RD + on-chip hardware timer that every 50ms to enter timer interrupt service program through SPI serial interface once A/D conversion and the converted data from the interface chip UART 74LBC176 converted to 485 signal sent first bit machine. Judging by the position machine control directives issued after the traction motors and traction control.

STC89C52RD + is STC company produces enhanced 51 single-chip, high reliability, strong anti-jamming.

In the product registration on the controller do electromagnetic compatibility test and found that using AT89C52 pass power pulse interference experiments and pilot projects for high-voltage discharge interference, STC89C52RD + can easily be passed. STC SCM reliability evident.

2.2 STC89C52RD + switch-based measurement and control

Bed body adopts the limit switch for each campaign trip to limit and avoid system out of control due to traction force is too large, an injury suffered, or spin, swing angle too large to be thrown off the bed-patients.

When the touch travel limit switches, relay control circuits will directly off the motor power supply enables the motor stops. Controller STC89C52RD + real-time detection of the signal, and quickly adds this information through the supremacy of 485 serial bus pass-bit machine. System software will stop the process and system reset. SCM system of 23 output switch quantity status locks exist 3 tablets 74HC377, make sure that the status of reliable output. Various output isolation via opto-couplers, zoom, driven ULN2803 relay switches to control the motor stops and combinations of actions.

Set the "emergency exit" button in the patient feel uncomfortable when its own press release, the system will prompt the traction and bed-flat.

When patients pressed "quick retreat" button after the SCM detected by 485 this news first-bit machine. System software to receive, to immediately stop the current process of traction, and issue the command, the MCU is control of the traction motor reverse lifting force of traction. If the bed is rotating tilted, you control the bed of Rotary. These measures greatly improves traction for system security and reliability, for the purposes of a medical device is to be considered.

Choose a STC89C52RD + as

A dedicated switch signal detection and control of the processor. This makes this part of the control procedures more concise, pure, easy to implement, can ensure the system is reliable and correct. If this task is merged into other controllers, will increase the software programming difficult, the process is more complicated, this is bound to reduce systems running reliability and security.

2.3 based on the rotation of the ARM processor S3C44B0X motion control

Medical devices operation requires low noise.

The system uses high efficiency, low noise type 220V high voltage and high power DC motors as bed body movement of executive bodies, to implement a bed of mechanical system multidimensional, multiaxial, multiple degrees of movement. For DC motor control using PWM mode. PWM drive adopts high-efficiency, high-power VMOS amplifier circuit. In embedded motor control processor choices, using Samsong company 32-bit RISC processor S3C44B0X arm core. The processor has dual serial port, 5 PWM timer, 8-channel 10-bit ADC, maximum clock speed 66MHz, excels motion control requirements.

PC via RS-485 bus campaign directives issued by the rotation in velocities angle parameters and parameter data.

Three degrees of rotation each corresponds to a PWM timer output. Rotation motor speed control by PWM duty cycle parameter adjustment. Speed control is an open-loop. Angle sensor selection of high-precision single-ring potentiometer. Potentiometer external 5V incentive, or 0-360 degree corresponds to 0-5V. In fact, only the range of 0-30 degrees. In this way, ARM PWM controller, actuator and angle sensor angle position measuring points constitute a closed-loop control circuit, the implementation of the rotation angle adjustment.