A drone brake system

Abstract

The application discloses a kind of unmanned plane brake systems, the system includes: electric rudder, automobile brake master cylinder, oil pressure sensor, brake oil pipe, brake caliper, multi-disc brake friction pair and controller.Electric rudder pushes automobile brake master cylinder and generates hydraulic pressure, pressure oil is transported to left and right landing gear brake caliper by independent oil pipe, and oil pressure sensor real-time feedback pressure to controller, forms closed loop control.Brake friction pair uses carbon ceramic brake disc and carbon ceramic brake pad, light in weight, high temperature resistant.All hydraulic core components of the application are automobile industry shelf products, single set cost is low, response time is short, pressure control precision is high, suitable for 1.5~5 tons class medium and large unmanned plane, compared with aviation special scheme cost is greatly reduced, development cycle is greatly shortened, with outstanding cost advantage and good market competitiveness.

Description

Technical Field

[0001] This invention belongs to the field of drone braking system technology, specifically relating to a low-cost, high-reliability drone braking system that uses an electric servo motor and an automotive brake master cylinder to construct a hybrid electromechanical-hydraulic drive. Background Technology

[0002] With the rapid development of the low-altitude economy driven by drones, medium and large-sized drones are increasingly being used in logistics, aerial surveying, and emergency rescue. As a core component of the landing gear, the braking system's performance directly affects the safety and stability of drone takeoff and landing. Existing drone braking systems are mainly divided into two categories: fully electric brakes (EMA) and electro-hydraulic brakes (EHA).

[0003] The all-electric braking system uses a motor to directly drive the piston, eliminating the need for a hydraulic circuit. However, its motor has a high peak current, and its weight increases significantly with the braking torque, making it unsuitable for medium to large UAVs weighing over 3 tons. The electro-hydraulic braking system uses a servo motor to drive a bidirectional pump or a ball screw-piston assembly, forming an integrated hydraulic unit. This system offers better performance, but its core hydraulic components are custom-made for aerospace applications, resulting in high unit costs, long development cycles, and high supply chain dependence, making it difficult to meet the large-scale production needs of low-cost civilian UAVs.

[0004] In addition, some low-cost braking solutions suffer from insufficient braking accuracy, slow response (response time > 0.3s), and high braking noise. Furthermore, existing metal friction pairs are heavy, conflicting with the lightweight design principles of drones and impacting their endurance.

[0005] Therefore, there is an urgent need for a braking system that meets the braking performance requirements of medium and large-sized UAVs, while also being low-cost, lightweight, and having a short development cycle. Summary of the Invention

[0006] The purpose of this invention is to address the shortcomings of existing technologies by providing a low-cost, highly reliable, fast-response, and lightweight UAV braking system, thereby overcoming the drawbacks of existing aviation-specific components, such as high cost, long development cycle, and heavy weight.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A drone braking system includes an electric servo motor, an automotive brake master cylinder, a hydraulic pressure sensor, brake lines, brake calipers, a multi-disc brake friction pair, and a controller.

[0009] The automotive brake master cylinder has a dual-chamber structure with two independent oil outlets. Its push rod is connected to the output end of the electric servo motor. The electric servo motor receives braking commands from the controller and outputs mechanical displacement to push the piston rod of the automotive brake master cylinder, generating hydraulic pressure. The pressurized oil is delivered to the brake calipers of the left and right landing gears through independent brake lines. An oil pressure sensor is installed on the pipeline between the automotive brake master cylinder outlet and the caliper to detect the oil pressure in real time and feed it back to the controller. The controller communicates with the flight control computer, receives the set oil pressure command, and controls the displacement of the electric servo motor in a closed loop based on the feedback value, ensuring that the actual oil pressure tracks the set oil pressure.

[0010] The multi-disc brake friction pair is made of carbon ceramic material, preferably consisting of two carbon ceramic brake discs and three carbon ceramic brake pads, forming four braking friction surfaces. The brake discs rotate with the wheel, and the brake pads are circumferentially fixed to the wheel axle through spline grooves and can move axially, achieving braking by being pushed by the caliper piston.

[0011] Compared with the prior art, the present invention has at least the following beneficial effects: 1. The core hydraulic components of this invention (brake master cylinder and oil pressure sensor) are all off-the-shelf products mass-produced in the automotive industry, significantly reducing costs. The electric servo motor, combined with the oil pressure sensor, enables closed-loop control with a measured response time of ≤0.15s and a steady-state pressure control accuracy of ±0.05MPa, demonstrating fast response speed and high control precision.

[0012] 2. The carbon-ceramic friction pair used in this invention weighs no more than 3 kg, approximately one-third the weight of the cast iron solution, which is beneficial for increasing the drone's endurance. Through servo position holding and pressure compensation strategies, the pressure decay within 30 seconds is ≤0.1 MPa, demonstrating strong dynamic pressure holding capability.

[0013] 3. All components used in the system of this invention are mature shelving products, requiring no custom development, with a short development cycle and a system integration cycle that can be shortened to less than 2 months. Attached Figure Description

[0014] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the overall structure of the drone braking system according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the automotive brake master cylinder structure in an embodiment of the present invention; Figure 3 This is a schematic diagram illustrating the working principle of the drone braking system according to an embodiment of the present invention; Figure 4 This is a flowchart of the closed-loop pressure control in an embodiment of the present invention. Detailed Implementation

[0016] The embodiments of the present invention will now be described in detail with reference to the accompanying drawings.

[0017] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0018] Example 1 This embodiment provides a drone braking system, specifically applied to a large fixed-wing drone with a maximum takeoff weight of 3.2 tons. For example... Figure 1 , Figure 3 As shown, the system mainly includes: electric servo motor 1, automotive brake master cylinder 2, hydraulic pressure sensor 3, brake oil pipe, brake caliper, brake friction pair and controller.

[0019] Electric servo motor 1 (see Figure 1 The electric servo motor 1 is used to receive braking commands and output mechanical displacement. Its rated torque is 1Nm~5Nm, and its rated power is 200W~500W. In this embodiment, the electric servo motor 1 has a power of 420W, a rated operating voltage of 24V, a rated speed of 1480rpm, a rated torque of 2.7Nm, and a rated current of 32A, which can meet the requirements of 0~10Mpa brake oil pressure output. The electric servo motor 1 integrates a position sensor with a position resolution of 0.0027°, enabling high-precision position control. The electric servo motor 1 communicates with the controller via a CAN bus to receive position commands from the controller.

[0020] The transmission connection between the electric servo motor 1 and the automotive brake master cylinder 2 can be any one of the following: direct push rod connection, linkage mechanism, or ball screw pair. In this embodiment, the output end of the electric servo motor 1 is connected to the piston rod 23 of the automotive brake master cylinder 2 via a mechanical push rod (this embodiment uses a linkage mechanism connection, but it is not limited to this). When the electric servo motor 1 receives a braking command, its output shaft rotates, driving the push rod to push the piston rod 23 of the automotive brake master cylinder 2 to produce axial displacement.

[0021] This embodiment uses an electric servo motor 1 as the driving element, instead of a traditional hydraulic servo valve or electric pump, because the electric servo motor 1 has the advantages of high position closed-loop control accuracy, fast response, and low cost. Combined with the feedback from the oil pressure sensor 3, the electric servo motor 1 can achieve high-precision displacement adjustment, thereby accurately controlling the output oil pressure of the brake master cylinder 2. The measured response time is ≤0.15s, which is far better than the 0.3s of existing low-cost solutions.

[0022] like Figure 1 , Figure 2 As shown, the automotive brake master cylinder 2 is a mature off-the-shelf product directly selected from the automotive industry, not a custom-made aerospace component. In this embodiment, the main cylinder diameter of the automotive brake master cylinder 2 is 15mm~30mm, the displacement is 5ml~20ml, and the maximum displacement is 22mm~30mm. Specifically, this embodiment uses a certain type of automotive brake master cylinder 2, made of cast iron, weighing 1.5kg, with a main cylinder diameter of 22.22mm, a displacement of 10.97ml, and a maximum displacement of 27mm. This automotive brake master cylinder 2 has a dual-chamber structure (see...). Figure 2 The first brake piston chamber 25 and the second brake piston chamber 26 are equipped with two independent pressure chambers, corresponding to two oil outlets: the first oil outlet 21 and the second oil outlet 22. The thread specification of the oil outlets is M10×1, and the oil pressure output by the two oil outlets is the same.

[0023] The upper end of the automotive brake master cylinder 2 is connected to an oil reservoir 28, which is used to replenish hydraulic oil during the piston's return stroke. The piston rod 23 of the automotive brake master cylinder 2 is pushed by the electric servo motor 1, compressing the hydraulic oil in the chamber to generate pressure. During braking, the piston rod 23 is compressed, compressing the hydraulic oil in the first piston chamber 25 and the second piston chamber 26 to generate braking pressure; when the brake is released, the piston rod 23 returns to its original position under the action of the electric servo motor 1, and the hydraulic oil in the oil reservoir 28 replenishes the chamber.

[0024] The master cylinder housing 24 of the automotive brake master cylinder 2 is also provided with an oil pressure sensor interface 27 for installing an oil pressure sensor 3.

[0025] The use of an automotive brake master cylinder (2) instead of an aviation-grade hydraulic cylinder in this embodiment of the invention is key to achieving low cost. The automotive brake master cylinder (2) has an annual production of millions of units, is technologically mature, has stable performance, and is inexpensive to purchase. Furthermore, its dual-chamber structure is naturally suited for independent oil supply to dual calipers, eliminating the need for an additional flow divider valve, simplifying the hydraulic piping, and reducing the risk of leakage.

[0026] The hydraulic pressure sensor 3 is a resistance strain gauge sensor with an accuracy of no less than 1.5%. It has an M10×1 external thread interface and is installed on the pipeline between the outlet of the automotive brake master cylinder 2 and the brake caliper via the hydraulic pressure sensor interface 27. The hydraulic pressure sensor 3 has a power supply voltage of 5V to 12V and an output voltage of 0.5V to 4.5V, which is proportional to the hydraulic pressure.

[0027] Its working principle is as follows: The elastic diaphragm of the oil pressure sensor 3 is in direct contact with the brake fluid. When the oil pressure increases, the diaphragm undergoes a slight elastic deformation, and the strain gauge attached to the back of the diaphragm is stretched or compressed accordingly, resulting in a change in resistance value. This breaks the bridge balance and outputs a voltage signal proportional to the oil pressure, which is transmitted to the controller.

[0028] In this embodiment of the invention, the oil pressure sensor 3 is the core feedback element for closed-loop control. By monitoring the output oil pressure of the vehicle's master brake cylinder 2 in real time, the controller can accurately determine the current brake pressure and compare it with the set pressure, driving the electric servo motor 1 to make dynamic corrections. The measured steady-state pressure control accuracy reaches ±0.05MPa, far exceeding the ±0.3MPa of a system without feedback. This accuracy ensures a stable output of braking torque, preventing wheel lock-up or insufficient braking force.

[0029] Brake calipers include left brake caliper 51 and right brake caliper 52 (see...) Figure 1 The main body of the brake caliper is made of high-strength aluminum alloy 7075 and is installed on the designated mounting position of the wheel axle with fastening screws. The brake caliper integrates hydraulic lines, one end of which is a hydraulic input interface connected to the outlet of the vehicle's master brake cylinder 2 via a brake oil pipe, and the other end is equipped with a bleed bolt for venting and sealing. The brake caliper contains caliper pistons 53 with a diameter of φ22mm, which are evenly distributed along the circumference to ensure uniform positive pressure is applied to the brake disc 61. In this embodiment, the left brake caliper 51 and the right brake caliper 52 each contain five caliper pistons 53.

[0030] When hydraulic oil enters the left brake caliper 51 and the right brake caliper 52, it simultaneously pushes all caliper pistons 53 out, squeezing the brake pads 62 and converting hydraulic energy into frictional torque.

[0031] The two outlets of the car's master brake cylinder 2 are connected to the brake calipers of the left and right main landing gear (i.e., left brake caliper 51 and right brake caliper 52) via independent brake hoses (high-pressure resistant rubber hoses or metal braided hoses), specifically as follows: Figure 1 As shown, the first oil outlet 21 is connected to the left brake caliper 51 via the first brake line 41, and the second oil outlet 22 is connected to the right brake caliper 52 via the second brake line 42. The oil pressure sensor 3 is installed on the pipeline between the oil outlet of the master cylinder 2 and the brake caliper, specifically near the master cylinder 2 for easy maintenance. Figure 1 As shown, the entire hydraulic pipeline has no unnecessary diverter valves, directional valves, or joints, making its structure extremely simple.

[0032] The automotive brake master cylinder 2 features dual-chamber independent outputs, with each chamber individually connected to a brake caliper, eliminating the need for complex valve assemblies and multiple connectors. This design not only reduces hydraulic pressure loss but also minimizes potential leak points, improving system reliability.

[0033] The brake friction pair has a multi-disc structure, such as Figure 3 As shown, it can be divided into a left brake disc friction pair and a right brake disc friction pair (corresponding to the left brake caliper and the right brake caliper, respectively). Each friction pair includes at least one set of carbon-ceramic brake discs and carbon-ceramic brake pads, installed between the wheel and the axle, and driven by the brake caliper to achieve braking. In this embodiment, as... Figure 1 As shown, the multi-disc brake friction pair consists of two 15mm thick carbon-ceramic brake discs 61 and three carbon-ceramic brake pads 62. The thicknesses of the three carbon-ceramic brake pads 62 along the axial direction are 13mm, 15mm, and 10.5mm respectively (from the brake caliper side to the wheel axle fixing side). The brake discs 61 and brake pads 62 are arranged alternately to form four brake friction surfaces. The carbon-ceramic material used in the multi-disc brake friction pair is a carbon fiber reinforced silicon carbide composite material (C / C-SiC), with a density of 2.0~2.3g / cm³, only 1 / 3 that of cast iron; it has an extremely low coefficient of thermal expansion, and hardly deforms at high temperatures; the coefficient of friction is greater than 0.3; and the maximum allowable operating temperature is up to 1200℃. The total weight of the brake friction pair does not exceed 3kg.

[0034] This embodiment employs a non-uniform thickness brake pad configuration: the brake pad closest to the brake caliper is 13mm thick, the middle brake pad is 15mm thick, and the brake pad furthest from the brake caliper (near the fixed end of the wheel axle) is 10.5mm thick. Since the middle brake pad contacts and rubs against the brake disc on both sides, it experiences higher heat load and wear rate; increasing its thickness to 15mm significantly improves wear resistance and extends service life. Conversely, the brake pad closest to the fixed end only operates on one side and experiences less stress; reducing its thickness to 10.5mm still meets strength requirements while also reducing overall weight. This non-uniform thickness configuration ensures a more even wear life for the three brake pads, avoiding the need to replace the entire friction pair due to premature failure of a single pad, further reducing maintenance costs.

[0035] The brake disc 61 is mounted on the wheel via a brake disc mounting bracket and rotates with the wheel. The brake pads 62 are circumferentially fixed to the axle via spline grooves, with no axial limit, allowing the brake pads 62 and brake disc 61 to move axially along the axle. During braking, the caliper piston 53 pushes the brake pads 62 to compress the brake disc 61, generating braking torque; when the brake is released, the caliper piston 53 returns to its original position, and the brake pads 62 separate from the brake disc 61.

[0036] The multi-disc carbon-ceramic brake friction pair of this invention achieves the goals of "low pressure, high torque, and low temperature rise." Taking this embodiment as an example, the total weight of the brake friction pair is only about 2.6 kg, a reduction of about 5 kg compared to the traditional cast iron solution, directly improving the drone's endurance. The four brake friction surfaces significantly increase the contact area, generating four times the braking torque under the same positive pressure compared to a single-disc brake. Therefore, the required hydraulic pressure is significantly reduced (maximum operating oil pressure is only 3 MPa), lessening the load on the electric servo motor 1 and the automotive brake master cylinder 2. Simultaneously, the excellent heat resistance of the carbon-ceramic material ensures that the temperature rise does not exceed 300°C under maximum braking conditions, avoiding brake failure caused by heat fade.

[0037] The controller can be an embedded controller based on an ARM Cortex-M4 core. It communicates with the flight control computer via a CAN bus and with the electric servo motor 1 via a CAN bus (or PWM / analog signal), and receives the analog voltage signal from the oil pressure sensor 3. The controller's sampling period is 10ms, and the control period is 20ms. The controller receives the set oil pressure command and uses closed-loop control of the electric servo motor 1's displacement based on the feedback value from the oil pressure sensor, ensuring that the actual oil pressure tracks the set oil pressure.

[0038] The braking system of this invention operates based on the electro-hydraulic pressure closed-loop control principle, and its control flow is as follows: Figure 3 , Figure 4 As shown below. (Combined with...) Figure 3 , Figure 4 Describe in detail each stage of the system from receiving the braking command to achieving stable pressure maintenance.

[0039] (a) Control command input and response stage When the flight control computer issues a braking command, the command is transmitted to the controller via the CAN bus in the form of a set oil pressure value P_set. The task scheduler inside the controller scans all input signals at a 10ms cycle. Simultaneously, the electric servo motor 1 receives position commands from the controller and executes the position commands corresponding to the set oil pressure. The electric servo motor 1 employs an electromechanical servo mechanism, whose internal position loop, speed loop, and current loop respond sequentially, precisely controlling the rotation angle and speed of the output shaft based on the magnitude and rate of change of the input electrical signal. This output, through a mechanical transmission mechanism (in this embodiment, a linkage mechanism), drives the piston rod 23 of the automotive brake master cylinder 2 to generate displacement.

[0040] (II) Hydraulic pressure generation and transmission stage The master cylinder 2 of the car brake system acts as the pressure source of the hydraulic system, and the movement of its piston rod 23 changes the internal volume of the pump. According to Pascal's principle, the pressure of a closed fluid increases uniformly under the compression of the piston, and the pressure change of the hydraulic oil follows the formula P = F / A, where P is the output pressure, F is the piston thrust, and A is the effective area of ​​the piston (in this embodiment, the cross-sectional area of ​​the master cylinder is approximately 3.88 cm²). The pressurized oil is synchronously delivered to the left brake caliper 51 and the right brake caliper 52 of the left and right main landing gears through independent first brake oil pipe 41 and second brake oil pipe 42.

[0041] (III) Braking Execution and Pressure Monitoring Phase After the hydraulic oil enters the brake caliper, it pushes all the caliper pistons 53 out synchronously, evenly pressing the carbon ceramic brake disc 61, converting hydraulic energy into braking friction torque. Simultaneously, the oil pressure sensor 3, installed on the outlet pipe of the car's brake master cylinder 2, collects the oil pressure value in real time and converts it into a standard voltage signal of 0.5V~4.5V, feeding it back to the controller. The sampling frequency of this signal is 100Hz, sufficient to capture transient pressure changes.

[0042] (iv) Feedforward position calibration and initial positioning Before actual use, the controller performs hydraulic pressure-stroke calibration. Specifically, the controller drives the electric servo motor 1 to move in a stepping manner, recording the feedback values ​​of the hydraulic pressure sensor 3 corresponding to different servo motor positions, and generating a calibration mapping table. For example, calibration data shows that when the set hydraulic pressure is 1.0 MPa, the corresponding stroke of the servo motor push rod is approximately 4.5 mm; when the set hydraulic pressure is 2.5 MPa, the corresponding stroke of the servo motor push rod is approximately 5.0 mm. This mapping table is stored in the controller.

[0043] When the flight controller issues a braking command, the controller directly looks up the estimated servo position command (feedforward) based on the set oil pressure P_set and immediately drives the electric servo 1 to move quickly to that position. At this time, the system oil pressure rises rapidly to close to P_set, but due to factors such as brake disc wear, elastic deformation of hydraulic lines, and high and low temperature environments, the actual oil pressure P_fb may deviate from P_set.

[0044] (v) Closed-loop control and dynamic adjustment stage (PID fine-tuning) After the electric servo motor 1 completes the feedforward positioning, the controller's internal PID control algorithm, with a cycle of 20ms, performs fine-tuning of the pressure deviation. For example... Figure 4 As shown, within each control cycle, the controller executes the following steps: Get the set oil pressure P_set, and read the current actual oil pressure P_fb from oil pressure sensor 3.

[0045] Calculate the deviation: e = P_set - P_fb.

[0046] Deviation judgment: If |e| is less than the set threshold (0.05MPa in this embodiment), the controller determines that the system has entered the pressure stabilization zone. At this time, the controller outputs a zero-position signal to the electric servo motor 1, and the electric servo motor 1 stops moving actively, but its internal servo system still outputs holding torque to counteract the pressure drop caused by minor leakage in the hydraulic system. The system enters the "pressure holding phase".

[0047] If |e| is greater than or equal to the set threshold, the controller inputs the deviation e into the PID controller. The PID algorithm calculates the position increment of the electric servo motor, which is then sent to the driver of electric servo motor 1 via the CAN bus. This drives electric servo motor 1 to move, and electric servo motor 1 rotates by the corresponding angle according to the increment. This changes the position of piston rod 23 via a mechanical push rod, thereby adjusting the output oil pressure. Oil pressure sensor 3 then collects the new pressure again, and the above steps are repeated to recalculate the deviation, forming a closed loop until the deviation is eliminated.

[0048] In this embodiment, the PID parameters are tuned as follows: proportional coefficient Kp = 1.2, integral coefficient Ki = 0.1, and derivative coefficient Kd = 0.03.

[0049] (vi) Specific implementation mechanism of dynamic pressure holding When the system is in the pressure holding phase (|e|≤0.05MPa), the controller simultaneously initiates an auxiliary monitoring task: the controller monitors the pressure drop rate at a frequency of 1Hz. If the pressure drop exceeds 0.1MPa within 30 seconds, or the instantaneous drop rate exceeds 0.05MPa / s, the controller determines that the pressure loss is caused by leakage or seal creep. At this time, the controller exits the pressure holding mode and re-enters the pressure regulation mode, driving the electric servo motor 1 to perform micro-feed (step size less than 0.01mm) to restore the pressure to the set value within ±0.02MPa, and then re-enters the pressure holding mode. In this embodiment, the measured pressure drop within 30 seconds is ≤0.1MPa. This mechanism ensures that during prolonged braking (such as deceleration after aborting takeoff), the braking pressure is always maintained at the required level and will not decrease due to leakage.

[0050] The controller in this embodiment integrates the electric servo motor 1, the hydraulic pressure sensor 3, and the automotive brake master cylinder 2 into a closed-loop hydraulic control unit. This unit can receive hydraulic pressure commands from the flight control computer and accurately output the required brake hydraulic pressure without the need for complex hydraulic control logic intervention from the flight control system. Actual test results show that closed-loop control enables the braking system to meet aviation-grade requirements in terms of response time, pressure accuracy, and dynamic pressure holding capability, while the cost is only 1 / 5 of that of dedicated aviation solutions.

[0051] The system described in this embodiment also implements a segmented braking hydraulic pressure control strategy based on the UAV's taxiing speed. This strategy is executed by the controller. The controller obtains the current taxiing speed through the flight control or wheel speed sensor and outputs the set hydraulic pressure P_set according to the following rules: High-speed section (taxiing speed greater than 25 m / s): Due to the large lift generated by the wings and the low ground pressure, the ground adhesion is low. The controller limits the set oil pressure to no more than 1.0 MPa to prevent the wheels from locking up.

[0052] Medium speed range (gliding speed between 10 and 25 m / s): At this speed, the ground pressure gradually increases, and the adhesion is improved. The controller controls the set oil pressure to rise at a slope of 0.5 to 1.0 MPa / s to 2.5 MPa (maximum design brake oil pressure), achieving smooth and efficient deceleration.

[0053] Low speed range (gliding speed below 10m / s): At this time, the ground adhesion reaches its maximum, and the controller maintains the set oil pressure at 2.5MPa (maximum design brake oil pressure) until the drone comes to a complete stop.

[0054] This embodiment's segmented braking strategy fully utilizes the characteristic of ground adhesion changing with speed, maximizing braking torque while ensuring no wheel lock-up, thereby shortening the braking distance. This embodiment was tested on a 3.2-ton UAV: ​​at an initial braking speed of 35 m / s on a dry runway, using the above segmented strategy, the braking distance did not exceed 400 meters (specifically less than 380 meters). If constant pressure braking (2.5 MPa throughout) is used, wheel lock-up is very likely at high speeds, leading to skidding; if low pressure braking is used, insufficient braking force at medium and low speeds results in a braking distance exceeding 500 meters. Therefore, segmented control can achieve excellent braking performance.

[0055] The system described in this embodiment has been installed on a 3.2-ton class large fixed-wing cargo UAV and has completed over 100 takeoff and landing tests. The main performance indicators are as follows:

[0056] Under the same load and runway conditions, the braking capability of this invention is on par with a certain type of purchased aircraft component, while the manufacturing cost per unit is reduced by about 100,000 yuan and the weight is reduced by about 35%.

[0057] Example 2 This embodiment shares the same basic structure and control principle as Embodiment 1, but applies the braking system to a 1.5-ton medium-sized fixed-wing UAV. This embodiment only adjusts some parameters based on the takeoff weight of the medium-sized UAV to demonstrate that the technical solution of this invention can be implemented within a wide parameter range.

[0058] The specific adjustments are as follows: Automotive brake master cylinder 2: A medium-sized automotive brake master cylinder is selected, with a master cylinder diameter of 19.05mm, a displacement of 6.8ml, and a maximum displacement of 22mm.

[0059] Electric servo motor 1: Power 200W, rated torque 1.5Nm, rated current 18A.

[0060] Multi-disc brake friction pair: Due to the reduced overall braking torque requirement, a 15mm thick carbon-ceramic brake disc 61 and two 10mm thick carbon-ceramic brake pads 62 are used to form two friction surfaces. The material is still C / C-SiC, and the total weight is approximately 1.8kg.

[0061] Maximum brake fluid pressure: 2.0MPa (because the aircraft is light and has less adhesion, high pressure is more likely to cause the brakes to lock up).

[0062] Performance test results: On a 1.5-ton drone, with an initial braking speed of 35 m / s on a dry runway, the braking distance is approximately 300 m; the response time is 0.13 s; the pressure control accuracy is ±0.05 MPa; and the total system cost is approximately 16,000 yuan.

[0063] This embodiment demonstrates that the braking system of the present invention is applicable not only to large UAVs of the 3.2-ton class but also to medium-sized UAVs of the 1.5-ton class, exhibiting good scalability. Experiments show that the braking system described in this embodiment is applicable to medium-to-large fixed-wing UAVs of the 1.5-5 ton class.

[0064] The drone braking system provided in this invention has all its core components that can be directly purchased from the automotive parts market without any custom processing. It has a short development cycle and extremely high industrial practicality and market promotion value.

[0065] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, various modifications and variations can be made to the embodiments of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A braking system for unmanned aerial vehicles (UAVs), characterized in that, include: Electric servo motors are used to receive braking commands and output mechanical displacement; The automotive brake master cylinder has a push rod that is connected to the output end of the electric servo motor to convert mechanical displacement into hydraulic pressure. The automotive brake master cylinder has a dual-chamber structure with two independent oil outlets. The two brake calipers are each connected to the two brake outlets via independent brake lines; A multi-disc brake friction pair includes at least one set of carbon-ceramic brake discs and carbon-ceramic brake pads, which are installed between the wheel and the axle and are driven by the brake calipers to achieve braking; The oil pressure sensor is installed on the brake fluid line to detect the brake fluid pressure in real time and send the feedback to the controller. The controller communicates with the flight control computer, receives the set oil pressure command, and controls the displacement of the electric servo motor in a closed loop based on the feedback value of the oil pressure sensor, so that the actual oil pressure tracks the set oil pressure. The aforementioned automotive brake master cylinder and hydraulic pressure sensor are both off-the-shelf products mass-produced in the automotive industry.

2. The UAV braking system according to claim 1, characterized in that, The multi-disc brake friction pair consists of two carbon-ceramic brake discs, each 15mm thick, and three carbon-ceramic brake pads. The thicknesses of the three carbon-ceramic brake pads along the axial direction are 13mm, 15mm, and 10.5mm, respectively. The brake discs and brake pads are arranged alternately to form four brake friction surfaces. The brake discs rotate with the wheel, and the brake pads are circumferentially fixed to the wheel axle through spline grooves and can move axially.

3. The UAV braking system according to claim 1, characterized in that, The main cylinder diameter of the automotive brake master cylinder is 15mm~30mm, the displacement is 5ml~20ml, and the maximum displacement is 22mm~30mm; the rated torque of the electric servo motor is 1Nm~5Nm, and the rated power is 200W~500W.

4. The UAV braking system according to claim 1, characterized in that, The oil pressure sensor is a resistance strain gauge sensor with an accuracy of not less than 1.5, and it is installed on the pipeline between the oil outlet of the car brake master cylinder and the brake caliper.

5. The UAV braking system according to claim 1, characterized in that, The controller implements the following closed-loop control: Compare the set oil pressure P_set with the current oil pressure P_fb fed back by the oil pressure sensor, and calculate the deviation e = P_set - P_fb; When |e| is less than the set threshold, the controller outputs a zero-position signal, and the electric servo motor enters the position holding mode. When |e| is greater than or equal to the set threshold, the controller calculates the position increment of the electric servo motor using the PID algorithm and drives the electric servo motor to move until the deviation is eliminated.

6. The UAV braking system according to claim 1, characterized in that, The controller controls the brake fluid pressure in segments according to the drone's gliding speed: High-speed section: When the coasting speed is greater than 25m / s, the set oil pressure is limited to no more than 1.0MPa; Medium speed range: When the coasting speed is 10~25m / s, the control oil pressure is increased to 2.5MPa at a slope of 0.5~1.0MPa / s; Low speed range: When the coasting speed is below 10m / s, maintain the maximum set oil pressure until stop.

7. The UAV braking system according to claim 1, characterized in that, The carbon ceramic material used in the multi-disc brake friction pair has a density of 2.0~2.3g / cm³, a friction coefficient greater than 0.3, and a total weight of the brake friction pair not exceeding 3kg.

8. The UAV braking system according to claim 1, characterized in that, The transmission connection between the electric servo motor and the automotive brake master cylinder can be any one of push rod direct connection, linkage mechanism or ball screw pair.

9. The UAV braking system according to claim 1, characterized in that, The brake caliper body is made of 7075 aluminum alloy, and the brake caliper has a built-in caliper piston with a diameter of φ22mm, which is evenly distributed along the circumference.

10. The UAV braking system according to claim 1, characterized in that, The system is applied to medium and large fixed-wing UAVs with a takeoff weight of 1.5 to 5 tons, and the braking distance is no more than 400 meters at an initial braking speed of 35 m / s.

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