Two-stroke piston engine air inlet control system and method based on steering engine angle feedback

Abstract

The invention discloses a two-stroke piston engine air inlet control system and method based on steering engine angle feedback, and relates to the technical field of aviation and power machinery. The system comprises a CAN bus digital feedback steering engine, an electronic control unit (ECU), a crankshaft position sensor, an oil injection control module and a mechanical throttle valve structure, and four throttle valves of the horizontally-opposed four-cylinder engine are controlled to act synchronously through linkage of the single steering engine. The control method is characterized in that an angle detection unit of the steering engine is used for collecting the rotation angle of an output shaft, the rotation angle is transmitted to an ECU through a CAN bus, the rotation angle is directly mapped into the opening degree of a throttle valve through a built-in program or algorithm of the ECU, and a traditional throttle valve position sensor (TPS) is omitted; the ECU calculates oil injection parameters by combining the crankshaft rotating speed and the phase signals, drives the oil injector to act, and meanwhile adjusts the opening degree of the throttle valve in real time through closed-loop control. The system structure can be simplified, the cost is reduced, the whole control system is more compact, the signal transmission reliability is improved, the response speed is increased, and the system is suitable for light aircraft power systems such as small unmanned aerial vehicles.

Description

Technical Field

[0001] This invention relates to the field of aviation and power machinery technology, specifically to an electronic control system for a two-stroke piston engine, and more particularly to an electronic control system and method that uses a servo angle signal to replace a traditional throttle position sensor for closed-loop control. Background Technology

[0002] In the field of electronic control for existing unmanned small aircraft piston engines, especially two-stroke engines, throttle control typically relies on an "electronic throttle" structure. This involves driving the throttle valve plate with a motor and using a high-precision potentiometer or Hall sensor (i.e., throttle position sensor, TPS) mounted on the valve shaft to monitor the valve plate opening in real time.

[0003] While this structure is mature, it has the following shortcomings in applications requiring miniaturization, low cost, and high reliability: 1. Structural redundancy and cost: Traditional electronic throttle assemblies integrate motors, reduction mechanisms and sensors, resulting in a large size. Furthermore, the sensor components increase manufacturing costs and potential points of failure. 2. Challenges in two-stroke control: The intake method of a two-stroke engine is different from that of a four-stroke engine. It usually adopts intake throttling or crankcase throttling, which requires more precise control of the intake volume. Traditional PID control often relies on complex lookup table methods, which limits the response speed. 3. Signal lag: In traditional systems, the engine electronic control system (ECU) sends commands to the drive circuit to drive the motor to rotate, and then the sensor feeds back the actual position. There is a signal lag caused by mechanical transmission gaps.

[0004] Therefore, in the power systems of unmanned aerial vehicles or light aircraft, how to simplify the structure of the intake control system of a two-stroke piston engine, reduce costs, and improve control response speed is a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] The purpose of this invention is to provide an electronic control system and method for a two-stroke engine based on servo motor angle feedback. The aim is to use the angle feedback signal of the servo motor itself as the basis for determining the throttle opening, thereby eliminating the need for a separate throttle position sensor, simplifying the system structure, and improving control accuracy and response speed.

[0006] The engine of this invention adopts a horizontally opposed four-cylinder structure, and the throttle valves of the four cylinders are synchronously controlled by a single servo motor. The electronic control system comprises: 1. Actuator: A UAVCAN bus digital feedback servo motor with a rated torque of 15 kg·cm; this servo motor has a built-in angle detection unit and CAN bus communication module, and has dual functions of mechanical drive and signal acquisition. The output shaft of the servo motor is rigidly connected to the engine throttle valve shaft through a transmission mechanism, and can drive the throttle valve to rotate and adjust the throttle valve opening according to the control commands issued by the ECU; 2. Signal feedback unit: The servo motor integrates an angle sensor to detect the rotation angle of the servo motor output shaft in real time, which serves as the corresponding characteristic signal of the throttle opening and encapsulates the angle data into the first CAN message through the CAN bus protocol; 3. Electronic Control Unit (ECU): The ECU establishes a bidirectional communication connection with the servo motor via a CAN bus; the ECU has a CAN bus communication interface, multi-channel signal acquisition and processing capabilities, and a built-in throttle opening conversion algorithm; the ECU receives the first CAN message and parses the actual rotation angle of the servo motor from it; the ECU directly maps this actual rotation angle to the actual throttle opening value, which serves as the reference signal for calculating the engine intake air volume; the ECU has a built-in remote control communication module and algorithm, which can receive throttle or throttle opening adjustment commands from the ground operator; 4. Crankshaft position sensor: The engine uses a Hall effect sensor, which is installed at the engine flywheel to collect the crankshaft speed and phase signals, providing a reference for the ECU to determine the engine working cycle and fuel injection timing; 5. Fuel Injection Control Module: The ECU combines the actual throttle opening value and the crankshaft phase signal to calculate the fuel injection timing and fuel injection pulse width, and drives the fuel injector to perform the action; the formula for the control module to calculate the required fuel injection quantity is: required fuel injection quantity = intake air volume × fuel injection correction coefficient × basic fuel injection pulse width, wherein the fuel injection correction coefficient is determined according to parameters such as engine cylinder head temperature and throttle opening, and the basic fuel injection pulse width is a preset fixed value; 6. Throttle body linkage mechanism: The throttle body of the engine is mounted on the cylinder intake port via a flange. The servo motor controls the opening of the four throttle butterfly valves simultaneously via a rocker arm, two tie rods, and two connecting rods to ensure the consistency of intake air for the four cylinders.

[0007] Furthermore, the control method of the electronic control system includes the following steps: 1. Signal mapping: During the system calibration phase, a mapping table is established between the servo motor rotation angle and the throttle valve opening, and stored in the ECU's memory unit; 2. Start-up initialization: After the engine starts, the ECU, servo motor, crankshaft position sensor and CAN bus transmission module complete self-test, and the servo motor drives the throttle valve back to the initial opening (preset idle opening, usually 5°-8°). 3. Real-time acquisition and transmission: During engine operation, the servo motor acquires the rotation angle signal of its own output shaft (corresponding to the throttle opening) in real time and transmits the first CAN message data frame to the ECU at a fixed frequency. The data frame contains information such as servo motor ID, angle value, and signal check code. At the same time, the crankshaft position sensor acquires the crankshaft speed and phase signal in real time and transmits it to the ECU. 4. Throttle opening determination: The ECU receives the first CAN message and calculates the current throttle opening by looking up the table; 5. Fuel Injection Calculation: The ECU calculates the intake air flow based on the throttle opening and, in conjunction with the engine speed determined by the crankshaft position sensor signal, calculates the required fuel injection quantity. 6. Closed-loop control: The ECU generates injection commands based on the calculation results, controlling the injectors to open and close at specific positions of the crankshaft angle; at the same time, the servo adjusts the throttle opening in real time according to the ECU's opening adjustment command (the driver's remote control signal second CAN message), forming a closed-loop control cycle of "servo angle acquisition - ECU calculation - injection control - opening adjustment - servo angle acquisition", ensuring that the engine can maintain the best operating state under different operating conditions; 7. Fault Diagnosis and Handling: During the control process, the ECU monitors the validity of the servo angle signal, the CAN bus communication status, and the crankshaft position sensor signal in real time. If the servo angle signal is lost or distorted, or the CAN bus communication is interrupted, or the crankshaft position sensor fails, the fault protection mechanism is immediately activated: the servo drives the throttle valve back to a safe opening (maintaining the idling or low-speed operation opening), cuts off part of the fuel injection channel (adjusted according to the fault type), stores the fault code, and issues a fault warning signal to ensure the safe operation of the engine.

[0008] Beneficial effects: 1. Simplified structure and reduced cost: This invention creatively uses the angle feedback signal built into the servo motor to replace the traditional throttle position sensor (TPS), eliminating the need for additional sensor hardware and its wiring harness, thus reducing the hardware cost and assembly complexity of the system. 2. High reliability: The angle detection inside the servo motor usually uses a high-precision potentiometer or encoder, and the signal is transmitted through a digital CAN bus, which has strong anti-interference ability, avoids noise interference in analog signal transmission, and improves the reliability of signal transmission. 3. Fast response speed: Since the intermediate mechanical transmission feedback link is eliminated, the servo angle signal can more directly reflect the state of the actuator, and the ECU can adjust the fuel injection strategy more quickly according to the actual opening, thus optimizing the transient response performance of the two-stroke engine. 4. High integration: Particularly suitable for small drone engines, which helps reduce overall weight and improve power-to-weight ratio; 5. Easy to upgrade and expand: The CAN bus supports multi-node expansion, and auxiliary sensors such as intake air temperature and oxygen sensors can be added to the existing system to further optimize the ECU control strategy; at the same time, the angle control parameters of the servo motor can be adjusted through ECU software calibration, which makes it easy to optimize the control logic according to the engine performance requirements, and has great upgrade potential. Attached Figure Description Figure 1 This is a system principle block diagram of the present invention; Figure 2 This is a diagram showing the main system configuration of the present invention; Figure 3 The throttle body linkage mechanism of the present invention. Detailed Implementation

[0009] The following will be combined with the appendix Figures 1-3 The technical solutions of the present invention have been clearly and completely described. Obviously, the described embodiments are only some embodiments of the invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0010] The corresponding part numbers in the attached diagram are as follows: 1- Engine body, 2- ECU, 3- CAN bus communication line between ECU and servo motor, 4- Crankshaft position sensor, 5- Injector, 6- Throttle body, 7- Servo motor, 8- Throttle body linkage mechanism.

[0011] Selection and determination of technical parameters of core components: 1. Engine body ( Figure 2 1): Employs a horizontally opposed four-cylinder two-stroke piston engine with a pre-set flange mounting surface at the cylinder intake for fixing the throttle body. Figure 2 (6) 2. Servo motor ( Figure 2 7): Select a UAVCAN bus digital feedback servo motor with a rated torque of 15 kg·cm. This servo motor has a built-in high-precision angle detection unit (using a precision potentiometer or encoder) and a CAN bus communication module. The angle detection accuracy is ≤ ±0.1° and the response time is ≤ 5ms. It has the integrated function of mechanical drive and angle signal acquisition to meet the fast adjustment requirements of the throttle valve of a two-stroke engine. 3. Electronic Control Unit (ECU) Figure 2 2): A dedicated UAV engine controller with multi-channel signal acquisition, CAN bus bidirectional communication, and remote control signal reception functions is adopted. A customized throttle opening conversion algorithm, fuel injection parameter calculation model, and fault diagnosis program are developed. Its communication interface is connected to the servo motor. Figure 2 7) Crankshaft position sensor ( Figure 2Signal format matching in section 4); 4. Crankshaft position sensor ( Figure 2 4): A Hall effect sensor is used, and the output signal is a digital pulse signal. It is installed on the pre-set mounting seat on the outside of the engine flywheel, and the gap between it and the flywheel gear ring is controlled between 0.5mm and 1.5mm to ensure accurate acquisition of crankshaft speed and phase signals. 5. Fuel injector ( Figure 2 5): Electromagnetic injectors are selected, with one injector corresponding to each cylinder. The injector's drive interface is connected to the ECU (Electronic Control Unit). Figure 2 The output channel of (2) is matched and installed in the engine intake manifold near the cylinder intake valve; 6. Mechanical throttle body structure ( Figure 3 8): Throttle body ( Figure 2 The 6th cylinder (type 6) is a four-cylinder integrated structure, rigidly connected to the engine block intake port via flange bolts; the throttle body linkage mechanism (… Figure 3 The servo (8) consists of one rocker arm, two pull rods, and two connecting rods, made of high-strength aluminum alloy. The connecting rod length is finely adjustable to ensure the stability of the servo motor. Figure 2 7) When driven, the four throttle butterfly valves operate synchronously, with an opening error ≤ ±0.5°; 7. Communication and connection components: CAN bus communication cable ( Figure 2 (3) Shielded twisted pair cable with a characteristic impedance of 120Ω is used to connect the ECU ( Figure 2 2) and servo motor ( Figure 2 7) Reduce electromagnetic interference.

[0012] System software calibration and initialization implementation: 1. Start the calibration software of the ECU (2 in Figure 2), establish a communication connection with the ECU, and enter the signal mapping calibration mode; 2. Send servo angle control commands through calibration software to gradually increase the servo (7 in Figure 2) from 0° (corresponding to the throttle being fully closed) to 90° (corresponding to the throttle being fully open), pausing for 1 second at every 0.5° interval. At the same time, use a high-precision angle meter to measure and record the actual throttle opening value corresponding to each servo angle. 3. Import the measured "servo angle - throttle opening" data set into the ECU, fit and generate a mapping table, and store it in the ECU's memory to ensure that the ECU can quickly look up the table and calculate the actual throttle opening based on the servo angle signal.

[0013] System startup initialization process: 1. Connect the system power supply and start the engine. Figure 2 1), ECU ( Figure 22) Automatically triggers a self-test program, sequentially checking the working status of its own microprocessor, CAN bus communication interface, and remote control communication module, while simultaneously sending signals to the servo motor ( Figure 2 7) Send a self-test command; 2. Servo motor ( Figure 2 7) After receiving the self-test command, it reports its own working status (whether the angle detection unit and CAN communication module are normal). 3. After the self-test passes, the ECU ( Figure 2 2) Towards the servo ( Figure 2 7) Send the initial opening command, and the servo motor drives the throttle body linkage mechanism ( Figure 3 (8) Synchronously return the four throttle valves to the preset idle speed opening (5°-8°, preferably 6° in this embodiment); the ECU simultaneously initializes the fuel injection control parameters, sets the basic fuel injection pulse width to 1.2ms (based on the engine displacement preset), completes the system initialization, and enters the idle speed state.

[0014] Real-time control process implementation: 1. Engine ( Figure 2 1) During operation, the servo motor ( Figure 2 The built-in angle detection unit (7) collects the output shaft rotation angle signal in real time, encapsulates the angle value, servo ID, and signal check code into a first CAN message data frame, and transmits it via the CAN bus communication line ( Figure 2 3) Transmitted to ECU ( Figure 2 (2) 2. Synchronously, the crankshaft position sensor ( Figure 2 4) Real-time acquisition of crankshaft speed and phase signals, continuously transmitted to the ECU ( Figure 2 (2) The ECU calculates the crankshaft speed through the pulse signal cycle and determines the engine working cycle (intake, compression, power, and exhaust strokes) through the pulse signal phase. 3. ECU ( Figure 2 2) After receiving the first CAN message, the validity of the data is first verified by the signal check code. If the verification passes, the actual rotation angle of the servo motor is parsed, and the "servo motor angle - throttle opening" mapping table in memory is called to calculate the current actual throttle opening value. If the verification fails, the message is discarded and the system waits for the next set of data. 4. ECU ( Figure 2 2) Based on the actual throttle opening value, combined with the preset intake flow calculation model (intake flow = throttle opening coefficient × crankshaft speed × intake temperature correction coefficient, where the intake temperature correction coefficient can be collected by the extended sensor, and the default value of 1.0 is temporarily used in this embodiment), the current engine intake volume is calculated. 5. ECU ( Figure 2Substituting into the fuel injection quantity calculation formula (2): Required fuel injection quantity = intake air volume × fuel injection correction coefficient × basic fuel injection pulse width, where the fuel injection correction coefficient is dynamically adjusted according to the engine cylinder head temperature (collected by the built-in temperature sensor), and the basic fuel injection pulse width is a preset fixed value of 1.2ms; simultaneously combined with the crankshaft position sensor ( Figure 2 4) The phase signal transmitted in the middle is used to determine the injection timing (in this embodiment, the injection timing is set to 15° crankshaft rotation angle before the top dead center of the intake stroke). 6. ECU ( Figure 2 2) Based on the calculated injection timing and injection pulse width, the fuel injector ( Figure 2 5) Send drive commands to control the injectors to open and close precisely at the specified crankshaft angle position, so as to achieve quantitative fuel injection and ensure that the engine air-fuel ratio is maintained near the target value; 7. When the ground operator sends a throttle / throttle adjustment command, the command is transmitted to the ECU via the remote control communication module. Figure 2 2); The ECU encapsulates it into a second CAN message data frame (containing information such as servo ID, target angle, and command priority), and sends it to the servo ( Figure 2 (7) and drives the output shaft to rotate, through the throttle body linkage mechanism ( Figure 3 8) This causes all four throttle valves to adjust synchronously to the target opening. 8. Servo motor ( Figure 2 (7) The adjusted angle signal is acquired in real time and fed back to the ECU via the first CAN message. Figure 2 (2) The ECU recalculates the intake air volume and fuel injection volume based on the new throttle opening, adjusts the fuel injection command, and forms a closed-loop control cycle of "servo angle acquisition - ECU calculation - fuel injection control - throttle opening adjustment - servo angle acquisition" to ensure that the engine can maintain the best operating state under different operating conditions.

[0015] Fault diagnosis and protection implementation: 1. ECU ( Figure 2 2) During the control process, three key signals are monitored in real time: servo motor ( Figure 2 7) Continuity and rationality of angle signals (angle mutations exceeding ±5° are considered abnormal), CAN bus communication lines ( Figure 2 Transmission status of (3) (three consecutive unreceived messages are considered communication interruption), crankshaft position sensor ( Figure 2 Signal integrity (4) (a continuous 100ms without a pulse signal is considered a fault); 2. When the loss or distortion of the servo angle signal is detected, the ECU ( Figure 2 2) Immediately activate the protection mechanism: send a signal to the servo motor ( Figure 27) Send a command to drive the throttle valve back to a safe opening (drive to a safe opening of 20°), store the fault code "0x001-Steering angle signal abnormal", and send a fault warning signal (audible and visual alarm) to the ground through the remote communication module. 3. When a CAN bus communication interruption is detected, the ECU ( Figure 2 2) Immediately activate the protection mechanism: send a signal to the servo motor ( Figure 2 7) Send a command to drive the throttle valve back to a safe opening (drive to a safe opening of 20°), store the fault code "0x002-CAN bus communication fault", and send a fault warning signal (audible and visual alarm) to the ground through the remote communication module. 4. When a crankshaft position sensor malfunction is detected, the ECU ( Figure 2 2) Immediately activate the protection mechanism: send a signal to the servo motor ( Figure 2 7) Send a command to drive the throttle valve back to a safe opening (drive to a safe opening of 20°), store the fault code "0x003 - Crankshaft position sensor fault", and send a fault warning signal (audible and visual alarm) to the ground through the remote communication module. 5. After troubleshooting, the operator can clear the fault code using the ECU calibration software, and the system will automatically return to normal closed-loop control mode.

Claims

1. An engine electronic control system based on servo angle feedback, characterized in that, include: A servo motor is used to drive the throttle valve, and the servo motor is connected to the ECU via a CAN bus; The servo motor is used to collect its own rotation angle and send it to the ECU; The ECU is used to receive the angle signal of the servo motor and use the angle signal directly as the basis for determining the throttle opening, thereby controlling the fuel injection timing and fuel injection quantity.

2. The electronic control system according to claim 1, characterized in that, The servo motor is a digital servo motor with a kilogram-centimeter rating of 15 kg·cm.

3. The electronic control system according to claim 1, characterized in that, The ECU obtains angle data by parsing the first CAN message sent by the servo motor, and then sends a second CAN message containing the target angle to the servo motor.

4. A control method for an electronic control system as described in any one of claims 1-3, characterized in that, include: Establish the mapping relationship between servo angle and throttle opening; Real-time reception of angle data transmitted by the servo motor via the CAN bus; The angle data is converted into throttle opening based on the mapping relationship; the injection parameters are calculated and injection is executed in conjunction with the crankshaft position signal.

5. The method according to claim 4, characterized in that, The horizontally opposed four-cylinder engine controls the throttle valves of the four cylinders to operate synchronously via a servo linkage mechanism.

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