A SMA wire based air valve control device

Abstract

The utility model relates to a fluid control technical field, concretely relates to a kind of air valve control device based on SMA wire.The utility model constructs closed loop control by microcontrol unit, current drive module and current feedback detection module, and current feedback detection module real-time sampling output is fed back to the current signal of SMA wire to microcontrol unit, and microcontrol unit is dynamically adjusted PWM control signal based on the feedback signal, and the precise calibration of output current is realized.Compared with the SMA wire air valve device of existing open loop control, the response delay of air valve opening and closing is significantly reduced, and the action is more timely.Meanwhile, closed loop control architecture can automatically correct the deviation caused by SMA wire aging, environmental temperature change or air path load fluctuation, without manual intervention, greatly improve the adaptive ability and long-term operation stability of device.

Description

Technical Field

[0001] This utility model relates to the field of fluid control technology, specifically to a valve control device based on SMA wire. Background Technology

[0002] Existing pneumatic valve control devices based on shape memory alloy wire (SMA wire) mostly employ constant voltage power supply or simple on / off switching control. Because the resistance of the SMA wire fluctuates significantly with temperature changes, the output current is highly unstable under constant voltage power supply mode. This makes it difficult to accurately control the heating rate and contraction amplitude of the SMA wire. Excessive current can cause overheating and damage to the SMA wire, shortening its service life; insufficient current will prevent the valve plate from fully opening, resulting in sluggish action and poor repeatability, severely affecting the reliability of pneumatic circuit control.

[0003] Furthermore, traditional SMA wire pneumatic valve control devices generally lack effective current feedback regulation mechanisms, and are mostly open-loop control architectures. They cannot monitor the current status output to the SMA wire in real time, nor can they dynamically correct drive parameters based on current fluctuations or load changes, further exacerbating the lack of control precision. These devices are ill-suited for applications requiring high control precision and operational stability, especially in portable medical devices and miniature pneumatic systems where reliability and miniaturization are paramount, where the limitations of existing technologies are even more pronounced.

[0004] Therefore, how to effectively solve the above-mentioned technical problems has become the core issue that this utility model urgently needs to address. Utility Model Content

[0005] To address the problems existing in current PC board wind deflector assemblies, this utility model provides an air valve control device based on SMA wire, comprising an inner liner, a support layer, and a buffer layer disposed outside the support layer; the support layer is in a fully arc shape, with both ends contacting and engaging with the outer edge of the inner liner, and a cavity is formed between the support layer and the inner liner; the buffer layer is located outside the support layer, with its edge fused to the inner liner, and the outer side of the support layer is embedded in the buffer layer.

[0006] The inner lining layer is provided with a stop block on the side corresponding to the support layer, and both ends of the support layer are located inside the stop block, thereby limiting the support layer through the stop block.

[0007] There are gaps between the two ends of the support layer and the stop block.

[0008] The top surface of the support layer is provided with multiple transverse ribs at intervals, and the ribs are embedded in the buffer layer.

[0009] The surface of the rib is provided with a hook layer, which is further embedded in the buffer layer.

[0010] The beneficial effects of this invention are as follows: This invention constructs a closed-loop control system through a microcontroller unit, a current drive module, and a current feedback detection module. The current feedback detection module samples the current signal output to the SMA wire in real time and feeds it back to the microcontroller unit. Based on this feedback signal, the microcontroller unit dynamically adjusts the PWM control signal to achieve precise calibration of the output current. Compared with existing open-loop controlled SMA wire air valve devices, the response delay of the air valve opening and closing is significantly reduced, and the action is more timely. At the same time, the closed-loop control architecture can automatically correct deviations caused by SMA wire aging, changes in ambient temperature, or fluctuations in air circuit load without manual intervention, greatly improving the device's adaptability and long-term operational stability. The microcontroller unit directly adjusts the output current through the PWM control signal. The high-frequency characteristics of the PWM signal combined with the real-time nature of the closed-loop feedback make the current adjustment response rapid, enabling quick control of the SMA wire's contraction and recovery actions, thereby achieving rapid opening and closing of the air valve plate. Compared with the stuttering problem of traditional mechanically driven air valves, this device has higher adjustment flexibility and can quickly adapt to the air circuit control requirements under different working conditions. Attached Figure Description

[0011] Figure 1 This is a schematic diagram of the overall structure of the air valve control device based on SMA wire in the embodiments of this application; Figure 2 This is a schematic diagram of the current drive module in an embodiment of this application; Figure 3 This application provides a schematic diagram of the PWM control signal in an embodiment. Detailed Implementation

[0012] The present application will be further described in detail below with reference to the accompanying drawings, so that those skilled in the art can better understand and implement the present invention, but the embodiments described are not intended to limit the present invention.

[0013] Example: Figure 1-3As shown, a valve control device based on SMA wire includes a microcontroller unit 100, a current drive module 200, an SMA wire actuator 300, and a current feedback detection module 400. The PWM output terminal of the microcontroller unit 100 is connected to the input terminal of the current drive module 200, and the output terminal of the current drive module 200 is electrically connected to the SMA wire in the SMA wire actuator 300. The SMA wire is fixedly connected to the valve mechanism. The sampling terminal of the current feedback detection module 400 is connected to the output circuit of the current drive module 200, and the signal output terminal of the current feedback detection module 400 is connected to the signal input terminal of the microcontroller unit 100. The microcontroller unit 100 adjusts the current output to the SMA wire through the PWM control signal to realize the contraction and recovery of the SMA wire, thereby driving the valve plate of the valve mechanism to open and close.

[0014] Specifically, the SMA wire actuator 300 includes a shape memory alloy wire (SMA wire) and a valve mechanism. The SMA wire is made of nickel-titanium alloy, with one end fixed to the valve plate connecting rod of the valve mechanism by a snap-fit, and the other end fixed to the fixed bracket of the device. The SMA wire is in a pre-stretched state. When an electric current is passed through the SMA wire and it is heated, it will undergo thermal contraction deformation, which will drive the valve plate connecting rod to push the valve plate open. When the current is cut off, the SMA wire will naturally cool down and return to its initial length, and the valve plate will close under the action of its own return spring.

[0015] In this embodiment, the microcontroller 100 can be an STM32 series microcontroller with a built-in PWM adjustment module. This module can output a stable pulse width modulation (PWM) signal, and the signal duty cycle is directly proportional to the current output to the SMA wire; that is, the larger the duty cycle, the larger the output current, and the smaller the duty cycle, the smaller the output current. This characteristic enables precise adjustment of the SMA wire drive current. The functions of the microcontroller 100 include receiving signals collected by sensors, outputting PWM control signals, and processing feedback signals from the current feedback detection module 400 to complete closed-loop control logic operations.

[0016] In one possible implementation, the PWM output terminal of the microcontroller unit 100 is connected to the gate of the semiconductor switch 203 in the current drive module 200 through a current-limiting resistor. In the current drive module 200, the output terminal of the switching power supply 201 is connected to the drain of the semiconductor switch 203, and the source of the semiconductor switch 203 is connected to one end of the SMA wire through the current sampling resistor, while the other end of the SMA wire is grounded. The sampling end of the current feedback detection module 400 is connected to the input end of the signal amplification module 202 via a wire, and the output end of the signal amplification module 202 is connected to the analog signal input end of the microcontroller unit 100, forming a closed-loop control circuit. The SPI communication pins of the sensor are connected to the corresponding SPI pins of the microcontroller unit 100 to realize signal acquisition and transmission; The microcontroller unit 100, current drive module 200, SMA wire actuator 300 and current feedback detection module 400 are all assembled on the device housing through plug-in interfaces or snap-fit ​​structures. There are no threaded connections between the modules, and they can be quickly disassembled and separated.

[0017] The current drive module 200 includes a switching power supply 201, a semiconductor switch 203, and a signal amplification module 202. The input terminal of the switching power supply 201 is connected to the microcontroller unit 100, and the output terminal of the switching power supply 201 is connected to the SMA wire via the semiconductor switch 203. The signal amplification module 202 is connected in series between the current feedback detection module 400 and the microcontroller unit 100.

[0018] In one possible implementation, the switching power supply 201 is selected as a DC-DC switching power supply 201 module with adjustable output voltage. Its input terminal is connected to the power control pin of the microcontroller 100 through DuPont wires and is controlled to start and stop by the microcontroller 100. The semiconductor switch 203 is a MOSFET. Its gate is connected to the PWM output terminal of the microcontroller 100, its source is connected to one end of the SMA wire via a wire, and its drain is connected to the output terminal of the switching power supply 201. It is used to receive PWM signals and control the current output to the SMA wire. The signal amplification module 202 is composed of an LM324 operational amplifier and external fixed resistors and capacitors. The non-inverting input terminal of the operational amplifier is connected to the signal output terminal of the current feedback detection module 400, the inverting input terminal is grounded through the feedback resistor, and the output terminal is connected to the analog signal input terminal of the microcontroller unit 100. It is used to amplify the current sampling signal to a voltage range that the microcontroller unit 100 can recognize.

[0019] The current drive module 200 can generate an adjustable constant current of 0-400mA to drive the SMA yarn actuator 300. By adjusting the duty cycle of the PWM signal, continuous adjustment within this current range can be achieved to meet the driving requirements of different contraction amplitudes and speeds of the SMA yarn.

[0020] In addition, the air valve control device also includes a sensor. The signal output terminal of the sensor is connected to the signal input terminal of the microcontroller unit 100 for signal acquisition. In one possible embodiment, the sensor is a pressure sensor, which is installed at the air outlet of the air valve mechanism. The signal output terminal of the sensor is connected to the corresponding communication pin of the microcontroller unit 100 via an SPI communication interface. The sensor is used to acquire the pressure signal in the air path in real time and convert it into an electrical signal, which is then transmitted to the microcontroller unit 100. This provides data for the microcontroller unit 100 to adjust the PWM signal duty cycle and control the opening and closing state of the air valve.

[0021] The current feedback detection module 400 includes a current sampling resistor, which is connected in series in the output circuit of the current drive module 200 for real-time sampling of the output current.

[0022] The current feedback detection module 400 includes a current sampling resistor as its core, connected in series in the output circuit of the current drive module 200, specifically between the source of the semiconductor switch 203 and the SMA wire. When current flows through the sampling resistor, a voltage drop proportional to the current magnitude is generated across the resistor. This voltage signal is the sampling signal, which is directly input to the input terminal of the signal amplification module 202 to achieve real-time sampling of the output current. In one possible implementation, such as... Figure 3 The PWM input capture timing diagram shows that the PWM signal duty cycle is proportional to the output current. The current rise phase corresponds to the SMA wire heating and contraction process, and the current fall phase corresponds to the SMA wire cooling and recovery process. By adjusting the PWM duty cycle and feedback control parameters, a fast and stable response for valve opening and closing can be achieved.

[0023] The working process of the air valve control device in this embodiment includes: after the device is powered on, the microcontroller unit 100 starts and completes the initialization configuration, including PWM adjustment module parameter setting, sensor communication protocol configuration, feedback signal acquisition channel calibration, etc., to ensure that each module is in a ready state; The sensor collects the pressure signal at the gas outlet in real time, converts it into an analog electrical signal and transmits it to the microcontroller unit 100. The microcontroller unit 100 performs analog-to-digital conversion and filtering on the signal to obtain real-time gas pressure data. Based on the collected pressure data and a preset pressure threshold, the microcontroller 100 outputs a PWM signal with a corresponding duty cycle through its built-in PWM adjustment module. For example, when the gas pressure is below the threshold, the microcontroller 100 increases the duty cycle of the PWM signal to increase the current output to the SMA wire. After receiving the PWM signal, the current drive module 200 outputs a stable voltage through the switching power supply 201. The semiconductor switch 203 periodically switches on and off according to the high and low levels of the PWM signal, thereby outputting an adjustable constant current of 0-400mA to the SMA wire. The SMA wire contracts under the heating action of the current, which drives the air valve plate to open and the air circuit is connected. The current sampling resistor collects the current signal output to the SMA wire in real time. The resulting voltage drop is amplified by the signal amplification module 202 and fed back to the microcontroller unit 100. The microcontroller unit 100 compares the feedback signal with the preset current value. If there is a deviation, it dynamically adjusts the duty cycle of the PWM signal to achieve closed-loop precise control of the current. The microcontroller unit 100 continuously receives pressure signals from the sensor. When the air pressure reaches a preset threshold, it reduces the duty cycle of the PWM signal until the current is cut off. After the SMA wire cools down, it returns to its original state, and the valve closes. The system then returns to the sensor sampling step and enters a cyclic control mode to ensure that the air pressure remains stable within the set range.

[0024] Traditional SMA wire valve control devices often employ constant voltage power supply or simple on / off switching methods. Because the resistance of the SMA wire fluctuates with temperature, constant voltage drive leads to unstable current, resulting in uncontrollable heating rate and contraction amplitude. Excessive current may cause overheating and damage to the SMA wire, while insufficient current will prevent the valve from fully opening, resulting in sluggish action and poor repeatability.

[0025] This embodiment addresses the aforementioned issues by employing a current closed-loop control method: the STM32 dynamically adjusts the PWM duty cycle based on feedback signals, keeping the output current constant at the target value. This ensures the SMA wire operates at its optimal current, resulting in a predictable and repeatable thermal response curve, avoiding overheating or underdrive phenomena. Furthermore, the closed-loop control automatically corrects the output based on load changes, enhancing the system's adaptability and long-term stability.

[0026] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A valve control device based on SMA wire, characterized in that, The device includes a microcontroller unit, a current drive module, an SMA wire actuator, and a current feedback detection module. The PWM output terminal of the microcontroller unit is connected to the input terminal of the current drive module, and the output terminal of the current drive module is electrically connected to the SMA wire in the SMA wire actuator. The SMA wire is fixedly connected to the air valve mechanism. The sampling terminal of the current feedback detection module is connected to the output circuit of the current drive module, and the signal output terminal of the current feedback detection module is connected to the signal input terminal of the microcontroller unit. The microcontroller unit adjusts the current output to the SMA wire through the PWM control signal to realize the contraction and recovery of the SMA wire, thereby driving the valve plate of the air valve mechanism to open and close.

2. The air valve control device based on SMA wire according to claim 1, characterized in that, The current drive module includes a switching power supply, a semiconductor switch, and a signal amplification module. The input terminal of the switching power supply is connected to the microcontroller unit, and the output terminal of the switching power supply is connected to the SMA wire via the semiconductor switch. The signal amplification module is connected in series between the current feedback detection module and the microcontroller unit.

3. The air valve control device based on SMA wire according to claim 1, characterized in that, It also includes a sensor, the signal output terminal of which is connected to the signal input terminal of the microcontroller unit for signal acquisition.

4. The air valve control device based on SMA wire according to claim 1, characterized in that, The current feedback detection module includes a current sampling resistor, which is connected in series in the output circuit of the current drive module for real-time sampling of the output current.

5. The air valve control device based on SMA wire according to claim 1, characterized in that, The device does not have a threaded riveting structure, and the microcontroller, current drive module, SMA wire actuator and current feedback detection module are detachably connected.

6. The air valve control device based on SMA wire according to claim 1, characterized in that, The microcontroller unit has a built-in PWM adjustment module, and the duty cycle of the PWM signal output by the PWM adjustment module is proportional to the magnitude of the current output to the SMA wire.

7. The air valve control device based on SMA wire according to claim 2, characterized in that, The current drive module can generate an adjustable constant current of 0-400mA to drive the SMA wire actuator.

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