Force Closed-Loop Control System Based on the Use of Voice Coil Motor and Beckhoff PLC Core Algorithm and Its Control Method

Abstract

The present invention discloses and provides a force closed-loop control system and its control method based on the use of a voice coil motor and the Beckhoff PLC core algorithm, which makes the force output more stable, can also adjust the force parameters in real time, and sets force and position threshold protection, enhancing the safety of the system. The present invention consists of a voice coil motor, a VCM driver, a power supply, a Beckhoff PLC controller, a force sensor, a signal amplifier, a pressing rod, and a mounting bracket; the power supply supplies power to the VCM driver, etc.; the Beckhoff PLC controller is respectively connected in feedback with the VCM driver and the signal amplifier; the force sensor is fixedly installed below the voice coil motor, and transmits the force sensor signal to the signal amplifier; the signal amplifier amplifies the force sensor signal and then transmits it to the Beckhoff PLC controller; the Beckhoff PLC controller sends corresponding control signals to the VCM driver according to the received force sensor signal, and then the VCM driver controls the voice coil motor. The present invention is applied to the technical field of force closed-loop control systems.

Description

Technical Field

[0001] The present invention relates to a force closed-loop control system, and particularly to a force closed-loop control system based on the use of a voice coil motor and the core algorithm of Beckhoff PLC and its control method. Background Art

[0002] A voice coil motor is a special form of direct drive motor. It has the characteristics of simple structure, small volume, high speed, high acceleration and fast response. Its working principle is that when a current-carrying coil (conductor) is placed in a magnetic field, a force will be generated, and the magnitude of the force is proportional to the current applied to the coil. Based on this principle, the motion form of the voice coil motor can be linear or circular arc, so such motors are divided into cylindrical voice coil motors and swing voice coil motors. The cylindrical voice coil motor series is quite widely used in the market. This kind of motor has a very high acceleration rate and can generate a powerful force of 0.7N - 1000N, while its stroke is less than 50mm. This type of motor is mainly used in medical, semiconductor, aviation, automotive and other fields, including valve brakes, small precision replacement measuring instruments, pressure detection, vibration platforms and active vibration damping systems and many other aspects. The cylindrical voice coil motor is adopted in this solution.

[0003] Compared with the well-known Siemens, Beckhoff is not well-known to the public. Although both are German brands, their styles are completely different. Siemens is overbearing. Neither its communication protocol nor its programming language is open, which makes people love and hate it; Beckhoff is all-inclusive, adopts the general Windows operating system, supports the standard IEC 61131-3 programming language, and the bus communication EtherCAT is also open.

[0004] Most of the implementation methods of the prior art are open-loop control. Most of the force control methods of voice coil motors adopt open-loop current control. Simply put, the driver makes the voice coil motor move according to different current values. When the motor movement stroke contacts the product to be measured, a force will be generated, and the force is controlled by controlling the current value of the voice coil motor. In the prior art, when the voice coil motor is used for pressure detection, the force control mostly adopts the open-loop current control method. This method cannot feedback the actual force value in real time, but can only return the current value, and under open-loop control, the current output cannot be changed in time according to the actual situation, resulting in insufficient force stability and poor controllability.

[0005] Of course, there are currently some closed-loop force control systems based on voice coil motor drives. For example, the Chinese patent application with the publication number CN211307555U discloses a closed-loop force control system based on a voice coil motor drive, which includes a base and a vertical support seat arranged on the base. It also includes an upper pressure head mechanism with a voice coil motor, a lower pressure head assembly, and a product conveying mechanism. The closed-loop force control system driven by the voice coil motor of the present invention is used for the binding of FPC and display screen. The voice coil motor is used to drive the movement of the binding upper pressure head structure. A force sensor is installed at the bottom of the lower pressure head structure. When the upper pressure head presses down, the force sensor continuously detects the force exerted by the upper pressure head and the lower pressure head on the bound product, and the applied force is fed back to the system by the sensed force. The system transmits the feedback information to the voice coil motor control system. The voice coil motor is in a closed-loop control system, and the pressure applied by the lower pressure head to the bound product can be automatically adjusted according to the data fed back by the force sensor to ensure the stability of the pressure received by the product during binding, so as to achieve rapid production. However, this system does not disclose what control means are used to achieve this. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a force closed-loop control system and its control method based on the use of a voice coil motor and the Beckhoff PLC core algorithm, so that the force output will be more stable, the force parameters can be adjusted in real time, and force and position threshold protection are set to enhance the safety of the system.

[0007] The technical solution adopted by the present invention is: The present invention includes a voice coil motor, a VCM driver, a power supply, a Beckhoff PLC controller, a force sensor, a signal amplifier, a pressure rod, and a mounting bracket;

[0008] The power supply supplies power to the VCM driver, the Beckhoff PLC controller, the signal amplifier board, the force sensor, and the signal amplifier respectively;

[0009] The Beckhoff PLC controller is respectively connected in feedback with the VCM driver and the signal amplifier;

[0010] The force sensor is fixedly installed below the voice coil motor and transmits the force sensor signal to the signal amplifier;

[0011] The pressure rod is fixed below the force sensor, and the device to be tested is located below the pressure rod;

[0012] The signal amplifier amplifies the force sensor signal and then transmits it to the Beckhoff PLC controller;

[0013] The Beckhoff PLC controller sends corresponding control signals to the VCM driver according to the received force sensor signal, and then the VCM driver controls the voice coil motor;

[0014] The mounting bracket provides support for each component.

[0015] The control method of the force closed-loop control system based on the voice coil motor and the Beckhoff PLC core algorithm is as follows: Set the input parameters; then start the force test, and then the Beckhoff PLC program starts to run. Before running, first detect whether the parameters are reasonable. If the parameters are abnormal, jump to the abnormal end and end this test; if the parameters are reasonable, enter the initialization of the force test module, and then control the VCM driver to move to the near point position, and detect the current motion state, that is, whether the motor shaft is normal and whether there is a value in the force sensor at this time. If the motion state is abnormal, jump to the abnormal end; if the motion state is normal, continue to move downward until the force sensor value change point is found, that is, the contact point between the pressing rod and the product to be tested. At the contact point between the pressing rod and the product to be tested, it will be judged whether it is within the range of force and position protection. If it is greater than the protection range, the motor shaft will stop immediately and return to the initial position, and then move downward at a low speed. The force sensor value gradually increases. When the sensor force value >= 5g, stop the motor shaft; after stopping, switch the motion mode of the VCM driver to the torque mode, then perform PID torque tuning, and start calculating the rise time; then judge whether the current pressure value reaches the set pressure value range. If it does not reach, continue PID tuning until the current pressure value reaches the set force range, then enter the steady state and start calculating the steady state time; when the steady state time is reached, switch the motion mode of the VCM driver to the position mode and move to the initial position; the process ends normally.

[0016] Further, the input parameters include the test force value, the steady state time, the PID parameter value, the initial position, the near point position, and the force and position protection parameters.

[0017] Further, the default mode of the torque mode is the position mode.

[0018] The beneficial effect of the present invention is that the force control method used by the present invention when using the voice coil motor for force detection adopts the position mode and the torque mode. Through the switching of the motion mode of the voice coil motor, first move to the near point of the product to be tested in the position mode, then switch to the torque mode, input the feedback force of the force sensor into the PID controller to adjust the torque in real time and output it to the VCM driver, and then switch to the position mode to return to the initial position after completion, so as to complete a force test.

[0019] Control method of the present invention: When controlling the voice coil motor to move downward in the Z direction through a Beckhoff PLC and contacting the product to be tested, a value appears on the pressure sensor. The feedback from the pressure sensor is sent to the Beckhoff PLC, and then the PLC performs PID tuning. The PID outputs parameters to the driver to control the movement of the motor. When the current pressure value reaches the set pressure value range, the holding time of the force is calculated. When the time of maintaining the current force reaches the steady state time, the motor rises to the initial position. The test is completed. By directly installing a force sensor below the voice coil motor, the force value can be fed back to the controller in real time, the real-time pressure value can be obtained, and the pressure waveform can be output. With the force feedback in the Beckhoff PLC, closed-loop control can be achieved. The force output under closed-loop control will be more stable, and the force parameters can be adjusted in real time. And force and position threshold protection are set to enhance the safety of the system. Description of the Drawings

[0020] Figure 1 is a schematic electrical connection diagram of the present invention;

[0021] Figure 2 is a schematic diagram of the test state of the present invention;

[0022] Figure 3 is a pressure waveform diagram of the present invention;

[0023] Figure 4 is a control flow chart of the present invention. Detailed Embodiment

[0024] I. The following are term explanations:

[0025] 1. PLC: Programmable Logic Controller (PLC).

[0026] 2. Beckhoff: Beckhoff, that is, Beckhoff Automation GmbH in Germany, mainly engaged in industrial automation production, a PLC manufacturer.

[0027] 3. PID: In process control, the PID controller (also known as the PID regulator) that controls according to the proportion (P), integral (I), and differential (D) of the deviation is the most widely used automatic controller. It has the advantages of simple principle, easy implementation, wide application range, independent control parameters, and simple selection of parameters; moreover, it can be proved theoretically that for the typical objects of process control - "first-order lag + pure lag" and "second-order lag + pure lag" control objects, the PID controller is an optimal control. The PID regulation law is an effective method for continuous system dynamic quality correction, and its parameter tuning method is simple and the structure can be changed flexibly (PI, PD,...).

[0028] 1. Rise time and steady state time

[0029] (1) Rise time refers to the time required for the pressure value to rise from 0 to (set pressure value - allowable error value);

[0030] (2) Steady-state time: the time during which the current pressure value is within the range of [set pressure value - allowable error value, set pressure value + allowable error value].

[0031] For example: The parameter values ​​of the force control waveform are set as: pressure value = 100g, steady-state time = 500ms, and the allowable error range is ±2% of the pressure value.

[0032] That is, the rise time is the time required for the pressure value to increase from 0g to 98g.

[0033] The steady-state time is when the pressure value is between 98g and 102g, the motor returns to zero position, and the force control process ends.

[0034] 2. Open-loop control and closed-loop control

[0035] (3) Open-loop control: A system control method without feedback information. When the operator starts the system and puts it into operation, the system transmits the operator's instructions to the controlled object at one time.

[0036] (4) Closed-loop control: A basic concept in control theory. It refers to a control relationship in which the controlled output is returned to the control input in a certain way and exerts a control influence on the input.

[0037] Difference: whether there is feedback; whether it has an effect on the current control. Open-loop control is generally a control activity that is completed in an instant, while closed-loop control must last for a certain period of time.

[0038] 3. Voice Coil Actuator / Voice Coil Motor is a device that converts electrical energy into mechanical energy and realizes linear and limited swing angle motion. It is a device that uses the interaction between the magnetic field from the permanent magnet and the magnetic poles in the magnetic field generated by the energized coil conductor to produce regular motion. Because the voice coil motor is a non-commutated power device, its positioning accuracy depends entirely on the feedback and control system and has nothing to do with the voice coil motor itself. With the use of appropriate positioning feedback and sensing devices, its positioning accuracy can easily reach 10NM, and the acceleration can reach 300g (the actual acceleration also depends on the condition of the load).

[0039] Second, the present invention is further described below with reference to the accompanying drawings and embodiments:

[0040] like Figure 1It is the pressure waveform result with a pressure value of 600 g and a steady-state time of 5000 ms. The rise time is 50 ms, and the pressure error value in the test is also within the normal error range.

[0041] As Figure 2 , Figure 3 shown, the force closed-loop control system based on the core algorithms of the voice coil motor and Beckhoff PLC includes a voice coil motor, a VCM driver, a power supply, a Beckhoff PLC controller, a force sensor, a signal amplifier, a pressure rod, and a mounting bracket;

[0042] The power supply supplies power to the VCM driver, the Beckhoff PLC controller, the signal amplification board, the force sensor, and the signal amplifier respectively;

[0043] The Beckhoff PLC controller is respectively connected in feedback with the VCM driver and the signal amplifier;

[0044] The force sensor is fixedly installed below the voice coil motor and transmits the force sensor signal to the signal amplifier;

[0045] The pressure rod is fixed below the force sensor, and the device under test is located below the pressure rod;

[0046] The signal amplifier amplifies the force sensor signal and then transmits it to the Beckhoff PLC controller;

[0047] The Beckhoff PLC controller sends corresponding control signals to the VCM driver according to the received force sensor signal, and then the VCM driver controls the voice coil motor;

[0048] The mounting bracket provides support for each component.

[0049] The product under test is the product to be pressed on the platform. The motor shaft, the pressure sensor, and the pressure rod are integrated and move in the up and down Z-axis direction.

[0050] Test description:

[0051] Initial position: That is, the safe position of the motor;

[0052] Proximal position: It refers to a position before the pressure rod contacts the product under test. In short, when moving to the position where the pressure rod contacts the product under test, there is still a certain gap between the pressure rod and the product under test and they are not in full contact. And because the heights of the products under test are slightly different, the proximal position needs to be considered well;

[0053] Force and position protection parameters: It refers to the maximum force value allowed by the sensor and the maximum position stroke protection of the axis. When any condition is triggered, the motor directly moves to the initial position to protect the sensor and the product under test;

[0054] PID Torque Tuning: Input Parameters: Current Force, Set Force, Maximum Output Torque Value, Minimum Output Torque Value;

[0055] Output Parameter: Torque Value

[0056] When the current feedback force << set force, the PID output torque value increases significantly;

[0057] When the current feedback force < set force, the PID output torque value increases slowly;

[0058] When the current feedback force = set force, the PID output torque value remains unchanged;

[0059] When the current feedback force > set force, the PID output torque value decreases slowly;

[0060] When the current feedback force >> set force, the PID output torque value decreases rapidly.

[0061] Set the input parameters, such as test force value, steady state time, PID parameter value, initial position, near point position, force and position protection parameters. Then start the force test, and then the Beckhoff PLC program starts to run. Before running, first check whether the parameters are reasonable (if the parameters are abnormal, jump to abnormal end and end this test). If the parameters are reasonable, enter the initialization of the force test module, and then control the VCM driver to move to the near point position, and detect the current motion state, that is, whether the motor shaft is normal and whether there is a value on the force sensor at this time (if the motion state is abnormal, jump to abnormal end). If the motion state is normal, continue to move down until the sensor value change point is found, that is, the contact point between the pressing rod and the product to be tested (when at the contact point between the pressing rod and the product to be tested, it will be judged whether it is within the range of force and position protection. If it is greater than the protection range, the shaft will stop immediately and return to the initial position), and then move down at a low speed. It can be seen that the sensor value gradually increases. When the sensor force value >= 5g, stop the shaft. After stopping, switch the motion mode of the driver to torque mode (the default mode is position mode), and then perform PID torque tuning and start calculating the rise time. Then judge whether the current pressure value reaches the set pressure value range. If not, continue PID tuning until the current pressure value reaches the set force range, then enter the steady state and start calculating the steady state time. When the steady state time is reached, switch the motion mode of the driver to position mode and move to the initial position. The process ends normally.

[0062] Compared with the prior art, the present invention has the following advantages:

[0063] 1. Real-time monitoring. With the force value feedback of the pressure sensor, it can better detect the pressure waveform and control;

[0064] 2. High stability. Using the closed-loop control method can make the whole system more stable and controllable.

[0065] 3. Strong applicability. And it can achieve a similar pressure effect by changing the PID parameters according to different products to be measured;

[0066] 4. Better pressure waveform effect. In the closed-loop control method, there will be no large overshoot and unstable pressure value in the pressure waveform;

[0067] 5. Safety. Force and position threshold protection are set to avoid damaging the sensor and the product to be measured.

[0068] Although the embodiments of the present invention are described with actual solutions, they do not constitute a limitation to the meaning of the present invention. For those skilled in the art, the modification of its implementation solutions according to this specification and the combination with other solutions are obvious.

Claims

1. A control method for a force closed-loop control system based on the core algorithms of a voice coil motor and a Beckhoff PLC. The force closed-loop control system using the core algorithms of a voice coil motor and a Beckhoff PLC consists of a voice coil motor, a VCM driver, a power supply, a Beckhoff PLC controller, a force sensor, a signal amplifier, a pressure rod, and a mounting bracket. The power supply supplies power to the VCM driver, the Beckhoff PLC controller, the signal amplifier board, the force sensor, and the signal amplifier respectively. The Beckhoff PLC controller is feedback-connected to the VCM driver and the signal amplifier respectively. The force sensor is fixedly installed below the voice coil motor and transmits the force sensor signal to the signal amplifier. The pressure rod is fixed below the force sensor, and the device to be measured is located below the pressure rod. The signal amplifier amplifies the force sensor signal and then transmits it to the Beckhoff PLC controller. The Beckhoff PLC controller sends corresponding control signals to the VCM driver according to the received force sensor signal, and then the VCM driver controls the voice coil motor. The mounting bracket provides support for each component, and it is characterized in that, The control method is as follows: Set the input parameters; then start the force test, and then the Beckhoff PLC program starts to run. Before running, first check whether the parameters are reasonable. If the parameters are abnormal, jump to the abnormal end and end this test; if the parameters are reasonable, enter the initialization of the force test module, and then control the VCM driver to move to the near point position, and detect the current motion state, that is, whether the motor shaft is normal and whether there is a value in the force sensor at this time. If the motion state is abnormal, jump to the abnormal end; if the motion state is normal, continue to move downward until the force sensor value change point is found, that is, the contact point between the pressing rod and the product to be tested. When at the contact point between the pressing rod and the product to be tested, it will be judged whether it is within the range of force and position protection. If it is greater than the protection range, the motor shaft will stop immediately and return to the initial position, and then move downward at a low speed. The force sensor value gradually increases. When the sensor force value >= 5g, stop the motor shaft; After stopping, switch the motion mode of the VCM driver to the torque mode, then perform PID torque tuning, and start calculating the rise time; Then judge whether the current pressure value reaches the set pressure value range. If it does not reach, continue PID tuning until the current pressure value reaches the set force range, then enter the steady state and start calculating the steady state time; When the steady state time is reached, switch the motion mode of the VCM driver to the position mode and move to the initial position; The process ends normally.

2. The control method of the force closed-loop control system based on the core algorithm of the voice coil motor and Beckhoff PLC according to claim 1, wherein: The input parameters include the test force value, the steady state time, the PID parameter value, the initial position, the near point position, and the force and position protection parameters.

3. The control method of the force closed-loop control system based on the core algorithm of the voice coil motor and Beckhoff PLC according to claim 1, characterized in that: The default mode of the torque mode is the position mode.

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