X-ray machine positioning method and system based on force sensor and brake current PWM closed-loop control

Abstract

According to the X-ray machine positioning method and system based on the force sensor and the brake current PWM closed-loop control, when the automatic positioning function of an X-ray machine bulb tube supporting system in a manual mode is achieved, the brake current is controlled through the PWM current closed-loop control method, and the brake force control precision is improved. According to the method, external force acting on the bulb tube supporting system by an operator is detected through a force sensor, so that interference is eliminated in the control method, and the positioning precision is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of automatic positioning of X-ray machines, and in particular to an X-ray machine positioning method and system based on a force sensor and a brake current PWM closed-loop control. Background Art

[0002] The current X-ray tube support system can achieve automatic positioning function in manual mode through mechanical positioning or electrical braking. In the mechanical positioning mode, the tube support system is manually dragged to move toward the target position. When the mechanical detection mechanism detects that the tube support system moves to within the error range of the target position, the mechanical positioning component is activated to stop the tube support system at the target position. In the electrical braking mode, the tube support system is manually dragged to move toward the target position. When the control unit detects that it is close to the target position, the control unit controls the power device to supply or cut off current to the electrical brake (generally an electromagnetic brake), thereby activating or disabling the electrical brake and stopping the tube support system near the target position.

[0003] The mechanical positioning method requires the installation of additional mechanical detection structures and mechanical positioning mechanisms. The mechanical detection mechanism is used to detect whether the ball tube support system has moved to the target position. The mechanical positioning mechanism is used to brake the ball tube support system to stop it at the target position when the ball tube support system moves to the target position. These additional components make the mechanical structure of the ball tube support system more complicated, increase the cost, and prolong the installation time.

[0004] Although the electrical positioning method does not require additional components, it also has its own problems. First, the positioning error is large. Because when the tube support system moves to the vicinity of the target position, it still has a certain speed, and the tube support system needs to support the tube and other related components, so it has a very large mass, even up to hundreds of kilograms. This speed and large inertia of the tube support system cause it to be unable to stop moving immediately even if the brake is activated, and it often passes the target position and stops outside the positioning error range. Secondly, if the brake is activated in advance when the tube support system moves to the target position, it is difficult to determine the advance time. When the tube support system is close to the target position, the operator still applies force to the tube support system, but because the force applied by different operators is different, this operating force is difficult to estimate, and the influence of other external forces such as friction makes it difficult to estimate the brake activation time in advance. Third, because the brake does not have PWM current closed-loop control, it can only provide the maximum braking force. The brake is generally an electric brake, and the control unit only controls it to open or close, so that the braking force it provides is maximum or zero, but it cannot provide a more appropriate braking force according to the motion state of the tube support system. Fourth, the current electrical positioning method is noisy. In the current method, when the ball tube support system moves near the target position, if the control unit activates the brake in advance, the speed of the ball tube support system decreases. The next control cycle detects its distance from the target position. If it is predicted that the ball tube support system cannot reach the target position, the electromagnetic brake will be released. The electromagnetic brake will be activated and released multiple times before the ball tube support system stops moving. In the current method, when the electromagnetic brake is activated, it is always activated with maximum current, and because the electromagnetic brake action surface and the brake force applied surface are usually rigid bodies, the collision contact between the two will generate a lot of noise. Fifth, during the braking process of the ball tube support system, the control unit does not consider external force interference such as the operating force applied to the ball tube support system by the operator in real time, resulting in poor positioning accuracy. Summary of the invention

[0005] In view of the problems existing in the above-mentioned prior art, the present invention provides an X-ray machine positioning method and system based on a force sensor and a brake current PWM closed-loop control. When realizing the automatic positioning function of the tube support system, the PWM current closed-loop control of the electromagnetic brake current is applied to control the magnitude of the brake force to generate a braking force of appropriate magnitude. In addition, the present invention also uses a force sensor to detect the operating force applied by the operator to the tube support system in real time to consider its influence on the automatic positioning of the tube support system.

[0006] The specific steps include:

[0007] Step 1: Determine the position sensor, force sensor, current sensor, control unit and other components. The position sensor is used to detect the real-time position of the tube support system and report this position to the control unit. It is installed on the motion transmission component of the tube support system; the force sensor is used to detect the operating force F applied by the operator to the tube support system. p , which is installed in the part of the ball tube support system that is touched by the operator, such as the push handle; the current sensor is used to detect the actual current of the electromagnetic brake, and it is installed in the electrical circuit of the electromagnetic brake; the control unit receives the signals from each sensor, and then calculates the PWM output of the control power device according to the following subsequent steps; the power device controls the current of the electromagnetic brake according to the PWM signal from the control unit, so that the electromagnetic brake outputs the corresponding braking force; the power supply component converts the input power provided by the system into the corresponding output power, and provides power to the control unit, power device, electromagnetic brake, various sensors and other electrical components.

[0008] Step 2: First, the control unit detects whether the real-time position of the tube support system has reached the starting position point M for applying the braking force. If it has not reached point M, the control unit does not enter the automatic positioning mode, does not start the control of the electromagnetic brake, and continues to monitor the real-time position of the tube support system; if it has reached or passed point M, the real-time position parameters of the tube support system are recorded and the automatic positioning mode is entered.

[0009] Step 3: The control unit receives the position sensor parameters, obtains the real-time position of the tube support system, and then calculates the movement speed v, acceleration a and distance s from the target position point B of the tube support system at this time.

[0010] Step 4: The control unit detects the force sensor parameters to obtain the operating force F applied by the operator to the tube support system p .

[0011] Step 5: The control unit calculates the braking force F required to be applied to the tube support system at this time according to the following formula: b :

[0012]

[0013] Among them, F r is the friction force on the ball tube support system, and m is the mass of the moving part of the ball tube support system.

[0014] Step 6: The control unit obtains the current required for the electromagnetic brake according to the functional relationship between the braking force and the braking current.

[0015] Step 7: The current sensor detects the actual current of the electromagnetic brake and outputs it to the control unit.

[0016] Step 8: The control unit compares the actual current of the electromagnetic brake with the required current of the electromagnetic brake calculated above to obtain the difference. After the difference is adjusted by PI, the duty cycle of the control power device is obtained, and then the control unit outputs a PWM signal according to the duty cycle to control the on and off of the power device. When the PWM output signal is at a high level, the power device is turned on, the voltage is applied to the electromagnetic brake winding, and the electromagnetic brake current increases; when the PWM output signal is at a low level, the power device is disconnected, the voltage is not applied to the electromagnetic brake winding, and the electromagnetic brake current decreases. Therefore, by controlling the on and off of the power device, the size of the actual current of the electromagnetic brake is controlled. Based on this, a negative feedback PWM closed-loop control of the electromagnetic brake current is formed, so that the actual current of the electromagnetic brake is approximately equal to the current required to generate the required braking force, thereby obtaining the required braking force.

[0017] Step 9: The control unit continues to detect whether the tube support system has reached the target position point B. If not, repeat steps 3 to 9; if it has reached the target position point B, exit the automatic positioning control mode, stop the PWM output, and fully activate the electromagnetic brake to completely lock the tube support system at the target position point B.

[0018] Beneficial effects: The present invention includes the following points. First, when the ball tube support system moves to the vicinity of the target position, the control unit controls the brakes in advance according to its movement speed and the distance from the target position so that it can stop at the target position. Secondly, the control unit will calculate the braking force value required for it to reach the target position based on the motion state parameters of the ball tube support system. Third, the present invention controls the electromagnetic brake current based on the PWM current closed loop to generate the braking force required by the ball tube support system, not just zero or maximum braking force. Fourth, the present invention detects the operating force of the operator on the ball tube support system through a force sensor. When calculating the braking force required for the ball tube support system to reach the target position, the influence of the operating force is taken into account, not just the braking force provided by the brake.

[0019] The present invention uses a PWM current closed-loop control method to control the electromagnetic brake current when realizing the automatic positioning function in the manual mode of the X-ray machine tube support system, thereby increasing the braking force control accuracy. The method also detects the external force applied by the operator to the tube support system through a force sensor, thereby eliminating its interference in the control method and improving the positioning accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is the force diagram of the ball tube support system;

[0021] Figure 2 This is the hardware control principle block diagram.

[0022] Figure 3Schematic diagram of the braking force control principle of the ball tube support system based on the force sensor.

[0023] Figure 4 This is a flow chart for the automatic positioning control of the ball tube support system based on the force sensor. DETAILED DESCRIPTION

[0024] The present invention is further explained below with reference to examples.

[0025] The present invention is used to realize the automatic positioning function of the tube support system in manual mode. Its basic force analysis and working principle are as follows Figure 1 As shown (the tube support system takes the suspension system as an example). Where m is the mass of the moving part of the tube support system, v is the speed of the tube support system at the real-time position point A, point A is the real-time position point of the tube support system, point B is the target position point, point M is the starting point for applying the braking force, s is the distance between points A and B, and F b is the braking force provided by the electromagnetic brake, F r is the friction force on the tube support system, F p It is the operating force applied by the operator to the tube support system.

[0026] In actual application, the operator pushes the tube support system to move along the suspension track toward the target position point B. When the control unit detects that the real-time position point A of the tube support system reaches point M, the control unit starts to enter the automatic positioning mode and continuously controls the electromagnetic brake to generate appropriate braking force according to the present invention. At this time, the tube support system is not only affected by the operating force F applied by the operator, but also by the operating force F applied by the operator. p , which is also affected by the braking force F provided by the electromagnetic brake b , friction force F r The effect of external forces.

[0027] Figure 2 The hardware control principle block diagram is shown in FIG. The position sensor is used to detect the real-time position of the tube support system, which can be installed on the motion transmission component of the tube support system; the current sensor is used to detect the electromagnetic brake current, which is located in the electrical circuit of the electromagnetic brake; the force sensor is used to detect the force applied by the operator to the tube support system, which can be installed on the part of the tube support system that is contacted by the operator; the electromagnetic brake is used to provide corresponding braking force for the tube support system, which is controlled by the power device; the power device provides a power circuit for the electromagnetic brake, which is controlled by the control unit; the control unit is the main control component, which accepts the parameters of each sensor, and then controls the power device according to the control method of the present invention to activate or disable the electromagnetic brake; the power supply component functions to convert the input power provided by the system into the corresponding output power, and provide power to the control unit, power device, electromagnetic brake, and various sensors and other electrical components.

[0028] exist Figure 3 In the control block diagram of the braking force (here, electromagnetic braking force), i b is the braking current calculated by the control unit based on the braking force required by the tube support system, i b * is the brake given current, i bf is the brake feedback current. F b =f(Ψ,i b ) is the functional relationship between braking force and braking current, which depends on the design parameters of the electromagnetic brake.

[0029] The basic control principle of the braking force is as follows: the control unit can calculate the motion parameters of the tube support system at this time, the motion speed v, the acceleration a and the distance s from the target position point B based on the real-time position parameters of the tube support system. Then, according to the basic principles of Newtonian mechanics, the required braking force F is calculated using the following formula b ,

[0030]

[0031] Then, the control unit obtains the given current i required for the electromagnetic brake according to the functional relationship between the braking force and the braking current. b *(t). This given current is compared with the actual current of the electromagnetic brake detected by the current sensor to obtain the difference between the two. After this difference is adjusted by PI, the duty cycle of the power device is obtained, and the control unit forms a PWM output signal based on this to control the on and off of the power device. When the PWM output signal is at a high level, the power device is turned on, the voltage will be applied to the electromagnetic brake winding, and the electromagnetic brake current will increase; when the PWM output signal is at a low level, the voltage will not be applied to the electromagnetic brake winding, and the electromagnetic brake current will decrease, thereby forming an electromagnetic brake current PWM closed-loop control, so that the actual current of the electromagnetic brake is approximately equal to the required given current. Therefore, by controlling the on and off of the power device, the size of the actual current of the electromagnetic brake is controlled. Based on this, a negative feedback PWM closed-loop control of the electromagnetic brake current is formed, so that the actual current of the electromagnetic brake is approximately equal to the current required to generate the required braking force, thereby obtaining the required braking force.

[0032] Figure 4 This is a flow chart of automatic positioning control of the ball tube support system based on the force sensor. When the ball tube support system moves along the track to the target position in manual mode, the control process is as follows:

[0033] 1) First, the control unit detects whether the real-time position point A of the tube support system has reached the starting position point M for applying the braking force. If it has not reached point M, the control unit does not start the control of the electromagnetic brake and continues to monitor the real-time position of the tube support system. If it has reached or passed point M, the real-time position parameters of the tube support system are recorded and the automatic positioning working mode is entered.

[0034] 2) In the automatic positioning working mode, the control unit updates the position sensor parameters, obtains the real-time position of the tube support system, and calculates the movement speed v, acceleration a and distance s from the target position point B of the tube support system at this time.

[0035] 3) The control unit then detects the output of the force sensor and obtains the operating force F applied by the operator to the tube support system. p .

[0036] 4) According to the basic principles of Newtonian mechanics and the parameters obtained above, the braking force required by the tube support system can be calculated as follows:

[0037]

[0038] 5) The control unit obtains the given current i required for the electromagnetic brake according to the functional relationship between the braking force and the braking current. b * .

[0039] 6) The current sensor detects the actual current of the electromagnetic brake and outputs it to the control unit.

[0040] 7) The control unit compares the actual current of the electromagnetic brake with the required given current calculated above to obtain the difference. After this difference is adjusted by PI, the duty cycle of the power device is obtained, and then the control unit outputs a PWM signal according to this duty cycle to control the on and off of the power device. When the PWM output signal is at a high level, the power device is turned on, the voltage is applied to the electromagnetic brake winding, and the electromagnetic brake current increases; when the PWM output signal is at a low level, the power device is disconnected, the voltage is not applied to the electromagnetic brake winding, and the electromagnetic brake current decreases. By controlling the on and off of the power device, the size of the actual current of the electromagnetic brake is controlled. Based on this, a negative feedback PWM closed-loop control of the electromagnetic brake current is formed, so that the actual current of the electromagnetic brake is approximately equal to the current required to generate the required braking force, thereby obtaining the required braking force.

[0041] 8) The control unit continues to detect whether the tube support system has reached the target position point B. If not, repeat the above steps 2) to 8); if it has reached the target position point B, exit the automatic positioning control mode, stop the PWM output, and fully activate the electromagnetic brake to completely lock the tube support system at the target position point B.

Claims

1. An X-ray machine positioning method based on force sensor and brake current PWM closed-loop control, characterized in that: The steps include: Step 1: Set up position sensors, force sensors, and current sensors; the position sensor is used to detect the real-time position of the tube support system; the force sensor is used to detect the operating force F exerted by the operator on the tube support system p ;The current sensor is used to detect the actual current of the electromagnetic brake; Step 2: The control unit detects whether the real-time position of the tube support system has reached the braking force application starting position point M. If it has not reached point M, the control unit does not enter the automatic positioning mode, does not start the control of the electromagnetic brake, and continues to monitor the real-time position of the tube support system; if it has reached or passed point M, the real-time position parameters of the tube support system are recorded, the automatic positioning mode is entered, and step 3 is executed; Step 3: The control unit receives the position sensor parameters, obtains the real-time position of the tube support system, and then calculates the movement speed v, acceleration a and distance s from the target position point B of the tube support system at this time; The control unit receives the force sensor parameters to obtain the operating force F applied by the operator to the tube support system. p ; Step 4: The control unit calculates the required braking force F applied to the tube support system at this time according to the following formula: b : Among them, F r is the friction force on the ball-tube support system, and m is the mass of the moving part of the ball-tube support system; Step 5: The control unit obtains the current required for the electromagnetic brake according to the functional relationship between the braking force and the braking current; Step 6: The current sensor detects the actual current of the electromagnetic brake and outputs it to the control unit; Step 7: The control unit compares the actual current of the electromagnetic brake with the current required by the electromagnetic brake to obtain the difference; after the difference is adjusted by PI, the duty cycle of the control power device is obtained, and then the control unit outputs a PWM signal according to the duty cycle to control the on and off of the power device; when the PWM output signal is at a high level, the power device is turned on, the voltage is applied to the electromagnetic brake winding, and the electromagnetic brake current increases; when the PWM output signal is at a low level, the power device is disconnected, the voltage is not applied to the electromagnetic brake winding, and the electromagnetic brake current decreases; accordingly, a negative feedback PWM closed-loop control of the electromagnetic brake current is formed, so that the actual current of the electromagnetic brake is approximately equal to the current required to generate the required braking force, thereby obtaining the required braking force; Step 8: The control unit continues to detect whether the tube support system has reached the target position point B. If not, repeat steps 3 to 8. If it has reached the target position point B, exit the automatic positioning mode, stop the PWM output, and fully activate the electromagnetic brake to completely lock the tube support system at the target position point B.

2. The X-ray machine positioning method based on force sensor and brake current PWM closed-loop control according to claim 1 is characterized in that: The position sensor is installed on the motion transmission component of the ball tube support system.

3. The X-ray machine positioning method based on force sensor and brake current PWM closed-loop control according to claim 1 is characterized in that: The force sensor is installed on the part of the tube support system that is touched by the operator.

4. The X-ray machine positioning method based on force sensor and brake current PWM closed-loop control according to claim 1 is characterized in that: The current sensor is installed in the electromagnetic brake electrical circuit.

5. An X-ray machine positioning system based on force sensor and brake current PWM closed-loop control, characterized in that: It includes a position sensor, a force sensor, a current sensor, a control unit, a power device and a power supply component; the position sensor is used to detect the real-time position of the tube support system and report this position to the control unit, which is installed on the motion transmission component of the tube support system; the force sensor is used to detect the operating force F applied by the operator to the tube support system p , which is installed in the part of the ball tube support system touched by the operator; the current sensor is used to detect the actual current of the electromagnetic brake, and it is installed in the electrical circuit of the electromagnetic brake; the control unit receives the signals of each sensor, and then calculates the PWM output of the control power device according to any method described in claims 1-4; the power device controls the current of the electromagnetic brake according to the PWM signal from the control unit, so that the electromagnetic brake outputs the corresponding braking force; the power supply component converts the input power provided by the system into the corresponding output power, and provides power to the control unit, the power device, the electromagnetic brake and each sensor.

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