CN111190376A - Proportional valve driving circuit suitable for agricultural machinery ECU and control method - Google Patents
Proportional valve driving circuit suitable for agricultural machinery ECU and control method Download PDFInfo
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- CN111190376A CN111190376A CN202010108448.0A CN202010108448A CN111190376A CN 111190376 A CN111190376 A CN 111190376A CN 202010108448 A CN202010108448 A CN 202010108448A CN 111190376 A CN111190376 A CN 111190376A
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B19/00—Programme-control systems
- G05B19/02—Programme-control systems electric
- G05B19/04—Programme control other than numerical control, i.e. in sequence controllers or logic controllers
- G05B19/042—Programme control other than numerical control, i.e. in sequence controllers or logic controllers using digital processors
- G05B19/0423—Input/output
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
- F16K—VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING
- F16K31/00—Actuating devices; Operating means; Releasing devices
- F16K31/02—Actuating devices; Operating means; Releasing devices electric; magnetic
- F16K31/06—Actuating devices; Operating means; Releasing devices electric; magnetic using a magnet, e.g. diaphragm valves, cutting off by means of a liquid
- F16K31/0675—Electromagnet aspects, e.g. electric supply therefor
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/20—Pc systems
- G05B2219/21—Pc I-O input output
- G05B2219/21001—Analog input
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/20—Pc systems
- G05B2219/26—Pc applications
- G05B2219/2601—Dispense machine glue, paste, flow
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- G—PHYSICS
- G05—CONTROLLING; REGULATING
- G05B—CONTROL OR REGULATING SYSTEMS IN GENERAL; FUNCTIONAL ELEMENTS OF SUCH SYSTEMS; MONITORING OR TESTING ARRANGEMENTS FOR SUCH SYSTEMS OR ELEMENTS
- G05B2219/00—Program-control systems
- G05B2219/20—Pc systems
- G05B2219/26—Pc applications
- G05B2219/2622—Press
Abstract
A proportional valve driving circuit and control method suitable for agricultural machinery ECU, including power amplification circuit, isolating the control chip of sampling circuit and agricultural machinery ECU; according to the current/opening corresponding relation of the electro-hydraulic proportional valve led into a control chip of an agricultural machinery ECU, when an opening driving part of the proportional valve needs to be adjusted to act, a corresponding current value is determined, and a power amplifying circuit is adjusted by controlling a PWM duty ratio to roughly adjust output current; the power amplifying circuit is also sequentially connected with a resistor and a proportional valve and controls the proportional valve; the sampling end of the isolation sampling circuit is connected to the sampling resistor, and the feedback end of the isolation sampling circuit is connected to the A/D sampling end of the control chip of the agricultural machinery ECU. The invention adopts a PWM mode to drive the coil of the electro-hydraulic proportional valve, outputs a 0-2.5A high-precision current signal through a power amplification chip, and drives the valve block of the proportional valve to move so as to drive an execution component on an agricultural machine.
Description
Technical Field
The invention discloses a proportional valve driving circuit suitable for an agricultural machinery ECU and a control method, and belongs to the technical field of agricultural machinery ECU equipment.
Background
The proportional electromagnet in the valve generates proportional electromagnetic force by means of input analog voltage signal to control the displacement of the valve core of the working valve, so as to control the size change of the valve port and complete the output of pressure and flow rate in proportion to the input voltage. The proportional valve driving circuit is mainly used for realizing accurate control of displacement or speed of hydraulic execution components such as a main clutch oil cylinder, a picking platform oil cylinder, a fruit picking box oil cylinder, a walking motor, a fruit picking motor and the like of the self-propelled agricultural machine through a proportional valve or a hydraulic motor. The driving circuit completes the conversion from the electric signal to the non-electric signal (speed, displacement and force), and realizes the power amplification of the small signal.
The ECU control board of the self-propelled agricultural machinery equipment needs to control a plurality of hydraulic execution components, and space resources between boards are limited due to the limitation of a shell, so that the circuit degree of the control board is high in integration and the circuit design is simplified as much as possible on the premise that each unit circuit of the ECU meets the control requirement. The special proportional valve amplifier equipped by the electro-hydraulic proportional valve manufacturer is expensive, large in size, multiple and complicated in power devices, and low in control precision due to the fact that no data acquisition and feedback loop exists; and because the proportional valve coil is an inductive load, the current proportional amplifier does not effectively eliminate voltage burrs loaded at two ends of the switching tube caused by the coil back electromotive force during the switching on and switching off of the MOSFET, so that serious electromagnetic interference is generated, and the service life of a driving device is further influenced.
Chinese patent document CN106896764B discloses a double-singlechip closed-loop control method for an industrial remote control receiver, where the industrial remote control receiver includes a power supply, a main singlechip, a sub-singlechip, an output amplification board, a relay and a radio frequency transceiver, and the closed-loop control method includes the steps of initializing the main chip, interrupting the reception of the main singlechip, determining the state of the sub-singlechip by the main singlechip, detecting the output by the sub-singlechip, detecting the state of the main singlechip by the sub-singlechip, and the like. The closed-loop design of the document can effectively avoid the occurrence of the events, and greatly improves the safety and the reliability. However, as can be seen from detailed reference, the patent document mainly realizes a remote closed-loop control algorithm through a double single chip microcomputer, and does not relate to the control of a proportional valve. This document does not describe any technical solutions or teachings regarding simplifying circuit design, reducing costs, avoiding electromagnetic interference, and extending the lifetime of the driving device.
Chinese patent document CN108312802B discloses an agricultural machinery vehicle body adjusting system, which realizes the adjustment of the vehicle body of the agricultural machinery by arranging a posture adjusting and torque distributing controller and corresponding devices on an agricultural machinery vehicle, and controls the movement of a hydraulic cylinder by a solenoid valve switch, and is simple and easy to operate. The method has the advantages that the PID closed-loop control is adopted, the feedforward signal correction is assisted, the adjustment precision and the adjustment frequency of the adjusting device are higher, and the control effect is better. The attitude signal is acquired in real time, so that the adjustment has real-time performance, and the practicability of the device is improved; the controller can control a plurality of paths of proportional solenoid valves, has a plurality of external sensor interfaces and supports a plurality of communication protocols, and can realize the control of posture adjustment and torque distribution of the hilly and mountain tractor by programming the controller. The patent document mainly makes patent requirements on the composition, the working process and the principle of each component of the body posture adjusting device of the agricultural machinery equipment, and each component is integrated and combined to work, and the deep design is not made on the electro-hydraulic proportional valve control circuit and the method.
Chinese patent document CN110024544A is an automatic row alignment control system and method for a rhizome crop harvester, which realizes real-time adjustment of the operation route of the harvester, thereby realizing the automatic row alignment function during the traveling process of the harvester. The automatic row alignment control system of the rhizome crop harvester comprises a signal acquisition module, a proportional valve driving module, a vehicle-mounted controller and a monitoring terminal, wherein the signal acquisition module comprises a left angle sensor, a right angle sensor and a displacement sensor, the left angle sensor and the right angle sensor are used for measuring offset data of a detection plate at a ridge, and the displacement sensor is used for measuring telescopic data of a hydraulic oil cylinder; the proportional electromagnetic directional valve drives a hydraulic oil cylinder to act, and the hydraulic oil cylinder is connected with the traction base of the harvester; the monitoring terminal and the vehicle-mounted controller transmit signals through the wireless communication unit; the input end of the vehicle-mounted controller is connected with the signal acquisition module, and the output end of the vehicle-mounted controller is connected with the proportional valve driving module.
The patent document takes the ridge row section trend as a research object, comprehensively applies key technologies in the fields of mechanical, hydraulic and electronic control and the like, and adopts a speed control mode based on PID to realize the real-time adjustment of the operation route of the harvester, thereby realizing the automatic alignment function of the harvester in the advancing process and further improving the automation level and the operation performance of the root crop harvesting machine. The harvester of the patent document outlines a row control system automatically, describes system components and a work flow in detail, and emphasizes on a control method, although components related to a proportional valve are involved, the relevant content of an actual control circuit of the proportional valve is not mentioned.
Chinese patent document CN203025507U discloses a synchronous seeder control system based on a hydraulic system, which transmits the rotational speed data of the implement to a single chip microcomputer through an implement rotational speed sensor, the single chip microcomputer gives an instruction to amplify and drive an electro-hydraulic proportional valve to move through D/a conversion, a hydraulic power source drives a hydraulic motor through the electro-hydraulic proportional valve, the hydraulic motor drives a seed metering device to perform seed metering operation, the rotational speed sensor of the seed metering device feeds back the single chip microcomputer through an a/D converter, and the single chip microcomputer sends an instruction to control the electro-hydraulic proportional valve to correct after comparing the feedback data of the implement travel speed sensor and the seed metering device rotational speed sensor, so as to achieve the purpose of synchronizing the implement travel speed and the seed metering.
The patent document briefly summarizes the working principle of the synchronous seeder control system of the hydraulic system, integrates various functional components and then logically describes the functions, and does not relate to the content of a proportional valve control circuit, a proportional valve control method and the like.
Disclosure of Invention
In view of the above technical deficiencies, the present invention provides a proportional valve driving circuit and a control method suitable for an agricultural machinery ECU.
Summary of the invention:
the invention adopts a PWM mode to drive the coil of the electro-hydraulic proportional valve, the drive circuit can receive a PWM small current signal output by the ECU, and outputs a 0-2.5A high-precision current signal through the power amplification chip to drive the valve block of the proportional valve to move so as to drive an execution component on the agricultural machinery.
The technical scheme of the invention is as follows:
a proportional valve driving circuit suitable for an agricultural machinery ECU is characterized by comprising a power amplifying circuit, an isolation sampling circuit and a control chip of the agricultural machinery ECU (the control chip of the agricultural machinery ECU is a CPU in figure 1);
the control chip of the agricultural machinery ECU is responsible for algorithm control and input/output port control, when the opening driving part of the proportional valve needs to be adjusted to act according to the electro-hydraulic proportional valve current/opening corresponding relation led into the control chip of the agricultural machinery ECU, the corresponding current value is determined according to a table look-up method, and the power amplification circuit is further adjusted by controlling the PWM duty ratio to roughly adjust the output current; the invention is to protect the detailed design scheme of the current closed-loop control circuit, only outlines the current closed-loop control algorithm, and does not belong to the technical content to be protected;
the power amplifying circuit is also sequentially connected with a resistor and a proportional valve and controls the proportional valve;
the sampling end of the isolation sampling circuit is connected to the sampling resistor, and the feedback end of the isolation sampling circuit is connected with the A/D sampling end of a control chip of the agricultural machinery ECU; because the ratio of the sampling current feedback to the output current of the power amplification circuit has high volatility and is not suitable for stable regulation and control of the output current, an additional sampling circuit is designed as an isolation sampling circuit. The sampling resistor and the isolation sampling circuit are used for realizing accurate acquisition of output current, and accurate adjustment of the output current of the proportional valve is completed through feedback data and a fuzzy self-adaptive PID control algorithm (the control algorithm is loaded in a control chip of an agricultural machinery ECU).
According to the invention, the proportional valve driving circuit suitable for the agricultural machinery ECU also comprises a port state sampling circuit, wherein the sampling end of the port state sampling circuit is connected with the proportional valve, and the feedback end of the port state sampling circuit is connected with the port state sampling end of a control chip of the agricultural machinery ECU;
the port state sampling circuit is used for judging the working state of the proportional valve coil: when the proportional valve coil is abnormal or damaged, providing a feedback signal; and the feedback current does not reach the set value all the time, and a control chip of the agricultural machinery ECU continuously adjusts PWM output.
According to the invention, preferably, the power amplification circuit adopts a two-way switch power chip as a driving device. And a double-path port in an actual circuit needs to be occupied so as to drive each hydraulic component of the agricultural machine.
According to the invention, the power amplification circuit adopts a VND5050AJ power switch chip as a driving device. The general power driving circuit is composed of resistors such as an amplifying circuit, an isolating circuit and a transistor driving circuit, and the selection of devices is complicated, and the requirements on overcurrent capacity and precision of each device are high. In order to reduce the layout size of the ECU controller and reduce the circuit complexity, the power amplification circuit in the invention adopts a VND5050AJ power switch chip as a driving device, limits the highest output current of 18A, completely meets the driving current requirement of the electro-hydraulic proportional valve, has wide driving voltage range (between 4.5V and 36V), and can simultaneously meet the requirement of 12V or 24V agricultural machinery equipment.
According to the invention, in the power amplification circuit adopting the VND5050AJ power switch chip, PWM0 is a PWM output port of a control chip of the agricultural machinery ECU, the control chip of the agricultural machinery ECU outputs a PWM waveform with adjustable duty ratio according to fixed frequency, and the driving current required by a proportional valve coil is generated through the switching amplification effect of the VND5050AJ power switch chip; AI _0 is a signal feedback port, generates a 0-3.3V voltage analog signal through an R11 voltage dividing resistor, then passes through a low-pass filter circuit consisting of a resistor R9 and a capacitor C7, converts a current signal fed back by a VND5050AJ power switch chip into a voltage signal and transmits the voltage signal back to an A/D acquisition port of the controller, and performs initial current sampling to form a closed loop.
According to the invention, the isolation sampling circuit adopts an optical coupling chip, and auxiliary operational amplifier circuits are added at two ends of the optical coupling chip to realize the amplification of input and output voltage signals. Because the linear optocoupler is used for isolating and amplifying current, and because an A/D feedback port is used for analog voltage, auxiliary operational amplifier circuits are required to be added at two ends of the optocoupler chip so as to amplify input and output voltage signals. Preferably, the optical coupler chip is an HCNR201 chip.
According to the invention, the port state sampling circuit preferably comprises a voltage division and current limitation circuit consisting of resistors R5, R6 and R7, and when the end B is disconnected, the port is defaulted to be a high level; when the end B is connected with the coil of the electro-hydraulic proportional valve, V is measured because the internal resistance of the coil of the electro-hydraulic proportional valve is generally between several ohms and is very small relative to a voltage division circuitStateAnd 0V, the port level is low at this time.
A proportional valve drive control method suitable for an agricultural machinery ECU is characterized by comprising the following steps:
the working method of the power amplifying circuit is that a control chip of an agricultural machinery ECU outputs a PWM waveform with adjustable duty ratio according to fixed frequency, and the driving current required by a proportional valve coil is generated through the switching amplification effect of a power switch chip; the signal feedback port generates a voltage analog signal through a divider resistor, then the voltage analog signal passes through a low-pass filter circuit, a current signal fed back by the power switch chip is converted into a voltage signal and is transmitted back to an A/D acquisition port of a control chip of the agricultural machinery ECU, and the current is sampled in a primary mode to form a closed loop;
the isolation sampling circuit adopts an optical coupling chip and auxiliary operational amplifier circuits added at two ends to realize the amplification of input and output voltage signals;
the port state sampling circuit comprises a voltage division and current limitation circuit consisting of resistors R5, R6 and R7, and when the end B is disconnected, the port is defaulted to be a high level; when the end B is connected with the electro-hydraulic proportional valve coil, the level of the port is low at the moment.
The technical advantages of the invention are as follows:
1. the invention simplifies the design complexity of the agricultural machine ECU circuit, can be simultaneously suitable for agricultural equipment with different battery voltages, reduces the proportion of the board distribution size of the ECU by more than 80 percent, and is beneficial to improving the heat dissipation area between boards.
2. The invention effectively restrains the peak pulse generated by the inductive load, improves the slope gradient of the proportional valve pulse, restrains the generation of EMI from the source, and effectively protects the switch power chip through the clamping voltage.
3. The invention adds a current acquisition and feedback circuit, and can improve the current precision of the proportional valve coil and shorten the overshoot time through a closed-loop control algorithm.
4. The invention adds a port state sampling circuit to detect the state of the proportional valve coil in real time, so that when the proportional valve coil is abnormally damaged, the control and other components can be found out in time, and the action of the proportional valve coil and other components can be stopped, and the alarm and maintenance can be given.
Drawings
FIG. 1 is a block diagram of a driving circuit according to the present invention;
FIG. 2 is a circuit diagram of a single-circuit control in the power amplifier circuit according to the present invention;
FIG. 3 is a schematic diagram of an isolated sampling circuit according to the present invention;
fig. 4 is a schematic diagram of a port state sampling circuit according to the present invention.
Detailed Description
The invention is described in detail below with reference to the following examples and the accompanying drawings of the specification, but is not limited thereto.
Examples 1,
As shown in fig. 1. A proportional valve driving circuit suitable for an agricultural machinery ECU comprises a power amplifying circuit, an isolation sampling circuit and a control chip of the agricultural machinery ECU (the control chip of the agricultural machinery ECU is a CPU in a figure 1);
the control chip of the agricultural machinery ECU is responsible for algorithm control and input/output port control, when the opening driving part of the proportional valve needs to be adjusted to act according to the electro-hydraulic proportional valve current/opening corresponding relation led into the control chip of the agricultural machinery ECU, the corresponding current value is determined according to a table look-up method, and the power amplification circuit is further adjusted by controlling the PWM duty ratio to roughly adjust the output current;
the power amplifying circuit is also connected with a resistor and a proportional valve in sequence and controls the proportional valve.
As shown in fig. 2. The general power driving circuit is composed of resistors such as an amplifying circuit, an isolating circuit and a transistor driving circuit, and the selection of devices is complicated, and the requirements on overcurrent capacity and precision of each device are high. The ECU controller is reduced in board layout size and circuit complexity. The power amplification circuit of the invention adopts a VND5050AJ power switch chip as a driving device, limits the highest output current to 18A, completely meets the driving current requirement of the electro-hydraulic proportional valve, has wide driving voltage range (between 4.5V and 36V), and can simultaneously meet the requirement of 12V or 24V agricultural machinery equipment. The chip is a two-way switch power chip, two-way ports in an actual circuit need to be occupied so as to drive each hydraulic component of the agricultural machine, and in order to simplify the design circuit, the unit only draws single-way control as an example for circuit explanation.
The PWM0 is a PWM output port of a control chip of the agricultural machinery ECU, the control chip of the agricultural machinery ECU outputs PWM waveforms with adjustable duty ratios according to fixed frequency, and the PWM waveforms generate driving current required by a proportional valve coil through the switching amplification effect of a VND5050AJ power switch chip. AI _0 is a signal feedback port, generates a 0-3.3V voltage analog signal through an R11 voltage dividing resistor, then passes through a low-pass filter circuit consisting of a resistor R9 and a capacitor C7, converts a current signal fed back by a VND5050AJ power switch chip into a voltage signal and transmits the voltage signal back to an A/D acquisition port of the controller, and performs initial current sampling to form a closed loop.
The current change range of the proportional valve coil is in a low-frequency range, high-frequency noise waves can be effectively filtered by a low-pass filter consisting of a capacitor C7 and a resistor R9, and the cut-off frequency is
Let R9 ═ 10K Ω, C7 ═ 100nF, fC159.2Hz to satisfy the range of current change of the coil of the hydraulic proportional valve. With simultaneous reference to VND5050AJ power switch chip data manual C _ SEN port feedback current coefficient
At different temperatures and different output currents IOUTFor example, the working current of the proportional valve of the self-propelled agricultural machine in the embodiment is within 2.5A, 2.7A is estimated as a protection current, and when the output current after proportional conversion exceeds 2.7A, the controller stops outputting the PWM waveform to protect the vehicle-mounted ECU.
The L _ load is an electro-hydraulic proportional valve coil load, and the PWM proportional valve drive circuit can cause the current in the L _ load to be drastically differentiated due to the high-frequency switching action of the L _ load as the L _ load is an inductive load, so that spike pulse and high-frequency oscillation voltage are generated, and electromagnetic interference is generated. The RCD absorption buffer circuit is formed by R12, D2, D1, R8 and C6 in the circuit to eliminate spike voltage, so that current flowing through the power chip and voltage at two ends are reduced, and the power chip is protected from being damaged. When the VND5050AJ power switch chip is turned off, the current in the proportional valve coilCan not disappear instantly to generate induced electromotive force ULThe voltage U across the VND5050AJ power switch chip is then loadedV＝U24V+UL，ULValue of (d) and rate of change of current (di) through the coilLDt) related to, diLThe greater the/dt, the greater the ULThe larger the value, the larger the value of UVThe larger the VND5050AJ power switch chip driving voltage ranges from 4.5-36V, so the chip is easily burned out.
R12 and D2 form a coil reverse freewheeling circuit, when a VND5050AJ power switch chip is turned off, a diode D2 is conducted under the action of induced electromotive force at two ends of the coil, and the current of the coil is consumed in the form of heat energy in the internal resistor R of the coil through a freewheeling circuit of the diodeLAnd resistor R12 to reduce iLThe value of (3) reduces the impulse voltage in the line, prolongs the on-off time of the coil, optimizes the current waveform and further inhibits the electromagnetic interference of the coil.
The capacitor voltage clamping circuit comprises an RCD clamping circuit consisting of D1, R8 and C6, when a VND5050AJ power switch chip is turned off, a diode D1 is turned on in the forward direction, a coil L _ load and a power supply charge a capacitor, voltage at two ends of the VND5050AJ power switch chip is clamped by the voltage of the capacitor, and meanwhile current flowing through the VND5050AJ power switch chip is dispersed into the capacitor; when the VND5050AJ power switch chip is turned on, the voltage drop between the VND5050AJ power switch chip 13 pin and the VND 8/9 pin is basically zero, the capacitor C6 passes through a current limiting resistor R8 and a VND5050AJ power switch chip stroke discharge circuit, and finally the energy of the capacitor is consumed in a resistor R8 in the form of heat energy. Through the RCD clamping circuit, spike pulse generated at the moment of turning off in the circuit is effectively restrained, the port voltage of the VND5050AJ power switch chip is clamped in a capacitor voltage range, and the VND5050AJ power switch chip is effectively protected.
The sampling end of the isolation sampling circuit is connected to the sampling resistor, and the feedback end of the isolation sampling circuit is connected to the A/D sampling end of the control chip of the agricultural machinery ECU.
As shown in fig. 3. In order to realize the accurate control of the coil current of the electro-hydraulic proportional valve, closed-loop control and a control algorithm of the current are required to be added. The VND5050AJ power switch chip has large fluctuation of the ratio of sampling current feedback to output current, is not suitable for output current stable regulation control, and needs an additional sampling circuit as shown in FIG. 3.
The isolation sampling circuit is designed by referring to an classical circuit in an HCNR201 optocoupler chip technical manual, the linear precision of the HCNR201 is 5% and is better than 15% of that of the HCNR200, the circuit is widely applied to an industrial signal acquisition system due to the high-quality linearity of the optocoupler, and because the linear optocoupler is used for isolating and amplifying current and an A/D feedback port of the controller is analog voltage, auxiliary operational amplifier circuits are required to be added at two ends of the HCNR201 to amplify input and output voltage signals. HCNR201 signal input current IFA feedback current Ipd1Output current Ipd2Input/feedback amplification factor of
An input/output amplification factor of
The gain G of the operational amplifier U1A is very large in the figure
Then the output voltage
So that the voltage gains and
the ratio is relevant.
A. Two collection points B are two ends of a sampling resistor R10 in the figure 1, and the coil current I of the electro-hydraulic proportional valveLThe working range is 0-2.5A, the voltage range of the A/D port is controlled to be 0-3.3V, in order to reduce the resistance power, the resistance value of the resistor R10 is selected to be as small as possible, and when the resistance value of R10 is 0.1 omega, the resistance power is controlled from Pr＝I2The maximum power can be found by R calculation to be 0.625W, and the amplification factor of the isolated sampling circuit is
10, therefore, the voltage range of the A/D sampling port of the controller is 0-2.5V when the R1 resistance is 100K and the R2 resistance is 10K, and the R10 is a 0.1 omega/1W chip power resistor. In the figure, a filter capacitor with a position of C3, R3 is a current resistor, and R4 and C4 form a low-pass filter for filtering high-frequency harmonics.
Examples 2,
The proportional valve driving circuit suitable for the agricultural machinery ECU according to embodiment 1, further comprising a port state sampling circuit, wherein a sampling end of the port state sampling circuit is connected with the proportional valve, and a feedback end of the port state sampling circuit is connected with a port state sampling end of a control chip of the agricultural machinery ECU;
the port state sampling circuit is used for judging the working state of the proportional valve coil: when the proportional valve coil is abnormal or damaged, providing a feedback signal; and the feedback current does not reach the set value all the time, and a control chip of the agricultural machinery ECU continuously adjusts PWM output.
As shown in fig. 4. The port state sampling circuit is used for detecting whether the output port of the driving circuit is in a normal state or not, feeding back to the controller and giving an alarm when the driving load is abnormal, and preventing that the feedback current does not reach a set value all the time when the coil load is damaged, and the controller continuously adjusts PWM output. In fig. 4, R5, R6, and R7 form a voltage dividing and current limiting circuit, the resistance of R5 is 20K Ω, the resistance of R6 is 2K Ω, and the resistance of R7 is 3.3K Ω, so when the terminal B is disconnected, the terminal V is turned offState2.9V, the port defaults to high; when the end B is connected with the coil of the electro-hydraulic proportional valve, V is obtained because the internal resistance of the coil is generally between a few ohms and is very small relative to a voltage division circuitStateAnd 0V, the port level is low at this time.
Claims (8)
1. A proportional valve driving circuit suitable for an agricultural machinery ECU is characterized by comprising a power amplifying circuit, an isolation sampling circuit and a control chip of the agricultural machinery ECU;
the control chip of the agricultural machinery ECU is responsible for algorithm control and input/output port control, when the opening driving part of the proportional valve needs to be adjusted to act according to the electro-hydraulic proportional valve current/opening corresponding relation led into the control chip of the agricultural machinery ECU, the corresponding current value is determined, and the power amplification circuit is adjusted by controlling the PWM duty ratio to roughly adjust the output current;
the power amplifying circuit is also sequentially connected with a resistor and a proportional valve and controls the proportional valve;
the sampling end of the isolation sampling circuit is connected to the sampling resistor, and the feedback end of the isolation sampling circuit is connected to the A/D sampling end of the control chip of the agricultural machinery ECU.
2. The proportional valve driving circuit suitable for the agricultural machinery ECU, according to claim 1, further comprising a port state sampling circuit, wherein a sampling end of the port state sampling circuit is connected with the proportional valve, and a feedback end of the port state sampling circuit is connected with a port state sampling end of a control chip of the agricultural machinery ECU;
the port state sampling circuit is used for judging the working state of the proportional valve coil: when the proportional valve coil is abnormal or damaged, providing a feedback signal; and the feedback current does not reach the set value all the time, and a control chip of the agricultural machinery ECU continuously adjusts PWM output.
3. The proportional valve driving circuit suitable for the agricultural machinery ECU according to claim 1, wherein the power amplification circuit adopts a two-way switch power chip as a driving device.
4. The proportional valve driving circuit suitable for the agricultural machinery ECU of claim 3, wherein the power amplification circuit adopts a VND5050AJ power switch chip as a driving device.
5. The proportional valve driving circuit suitable for the agricultural machinery ECU of claim 4, wherein in the power amplification circuit adopting the VND5050AJ power switch chip, PWM0 is a PWM output port of a control chip of the agricultural machinery ECU, the control chip of the agricultural machinery ECU outputs a PWM waveform with adjustable duty ratio according to fixed frequency, and the driving current required by a proportional valve coil is generated through the switching amplification effect of the VND5050AJ power switch chip; AI _0 is a signal feedback port, generates a 0-3.3V voltage analog signal through an R11 voltage dividing resistor, then passes through a low-pass filter circuit consisting of a resistor R9 and a capacitor C7, converts a current signal fed back by a VND5050AJ power switch chip into a voltage signal and transmits the voltage signal back to an A/D acquisition port of the controller, and performs initial current sampling to form a closed loop.
6. The proportional valve driving circuit suitable for the agricultural machinery ECU according to claim 1, wherein the isolation sampling circuit adopts an optical coupling chip, and an auxiliary operational amplifier circuit is added at two ends of the optical coupling chip to amplify the input and output voltage signals, preferably, the optical coupling chip is an HCNR201 chip.
7. The proportional valve driving circuit suitable for the agricultural machinery ECU according to claim 2, wherein the port state sampling circuit comprises a voltage division and current limitation circuit consisting of resistors R5, R6 and R7, and when the end B is disconnected, the port is defaulted to be a high level; when the B end is connected with a coil of the electro-hydraulic proportional valve, V isStateAnd 0V, the port level is low at this time.
8. A proportional valve drive control method suitable for an agricultural machinery ECU is characterized by comprising the following steps:
the working method of the power amplifying circuit is that a control chip of an agricultural machinery ECU outputs a PWM waveform with adjustable duty ratio according to fixed frequency, and the driving current required by a proportional valve coil is generated through the switching amplification effect of a power switch chip; the signal feedback port generates a voltage analog signal through a divider resistor, then the voltage analog signal passes through a low-pass filter circuit, a current signal fed back by the power switch chip is converted into a voltage signal and is transmitted back to an A/D acquisition port of a control chip of the agricultural machinery ECU, and the current is sampled in a primary mode to form a closed loop;
the isolation sampling circuit adopts an optical coupling chip and auxiliary operational amplifier circuits added at two ends to realize the amplification of input and output voltage signals;
the port state sampling circuit comprises a voltage division and current limitation circuit consisting of resistors R5, R6 and R7, and when the end B is disconnected, the port is defaulted to be a high level; when the end B is connected with the electro-hydraulic proportional valve coil, the level of the port is low at the moment.
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