Design method of liftable rear suspension system of amphibious vehicle

Abstract

The invention discloses a design method of a liftable rear suspension system of an amphibious vehicle. The design method comprises the following steps: S1, calculating parameters of a liftable rear suspension transmission mechanism; s1.1, calculating and checking a motor of the amphibious vehicle; s1.2, the size of the worm is calculated; s2, design and parameter selection of a damper: S2.1, parameter selection of a damping spring; s2.2, designing and calculating an elastic element; s2.3, a shock absorber is designed; and S3, designing a liftable rear suspension structure of the amphibious vehicle. By improving the mechanical structure design of the suspension, the amphibious vehicle can better adapt to different terrains and water environments and has higher driving performance, control stability and passing performance, and therefore the application field and task execution capacity of the amphibious vehicle are expanded.

Description

Technical Field

[0001] The invention belongs to the technical field of amphibious vehicle research, and in particular relates to a design method for a liftable rear suspension system of an amphibious vehicle. Background Art

[0002] As a new type of transportation that combines the functions of a land vehicle and a water boat, an amphibious vehicle can play its unique role on land, water, and the border area between land and water. Its appearance has changed our cognition and understanding of traditional vehicles and ordinary ships. In addition, the unique capabilities of amphibious vehicles are also of great significance to my country's coastal defense and border patrols, and can effectively solve certain sudden and complex problems. Amphibious vehicles can also be widely used in tourism, aquaculture and fishing and other daily production, geological exploration, and flood prevention and disaster relief work.

[0003] Existing suspension systems for amphibious vehicles often have problems with insufficient stability and adjustability. When driving on land, the suspension system needs to have sufficient suspension travel and appropriate stiffness to ensure the stability and comfort of the vehicle on uneven ground. However, due to the limitations of traditional suspension systems, vehicles are prone to stability problems such as tire loss of contact and vehicle shaking when encountering large uneven roads. When driving in water, the suspension system needs to have a certain buoyancy and stability to ensure that the vehicle can drive and control smoothly. However, there is still room for improvement in the stability and adjustability of existing suspension systems for driving on water. Secondly, existing suspension systems for amphibious vehicles have certain limitations in terms of passing performance. Passability refers to the ability of amphibious vehicles to pass under various terrain conditions, including climbing, off-roading, passing obstacles, etc. However, traditional suspension systems often cannot meet the passing requirements of vehicles in complex terrains, and cannot provide sufficient ground clearance and twisting capacity to cope with the challenges of various terrains.

[0004] In addition, the existing suspension system lacks adaptability and cannot automatically adjust the suspension stiffness and travel according to the changes in terrain, thus limiting the passing performance of amphibious vehicles in complex terrain. Finally, the existing amphibious vehicle suspension system needs to improve its ability to protect occupants and loads. Amphibious vehicles are usually used to perform special tasks, and the safety of occupants and loads is crucial. However, the traditional suspension system has certain limitations in shock absorption and buffering, and cannot effectively reduce the impact of bumps and vibrations on occupants and loads during driving. In addition, the protection capability against external shocks and unexpected situations also needs to be further improved. Amphibious unmanned platforms are mainly used to replace amphibious manned platforms to complete high-risk amphibious combat missions in harsh environments and confrontation conditions, and to improve the amphibious combat response speed. There are significant differences in the platform control method from amphibious manned platforms, which can make its water performance indicators reach higher, but in terms of amphibious function positioning and configuration layout, maneuvering principles and hydrodynamic characteristics, etc., they can fully draw on the research results of amphibious manned platforms for design.

[0005] Therefore, we propose a design method for a liftable rear suspension system of an amphibious vehicle to solve the above problems. Summary of the invention

[0006] The technical problem to be solved by the present invention is to provide a design method for a liftable rear suspension system of an amphibious vehicle.

[0007] The objective of the present invention is achieved through the following technical solutions:

[0008] A design method for a liftable rear suspension system of an amphibious vehicle comprises the following steps:

[0009] S1. Calculation of transmission mechanism parameters of the liftable rear suspension;

[0010] S1.1、Calculation and verification of electric motors for amphibious vehicles;

[0011] S1.2, Calculation of worm dimensions;

[0012] S2. Design and parameter selection of shock absorber:

[0013] S2.1, parameter selection of shock absorbing spring;

[0014] S2.2, design calculation of elastic elements;

[0015] S2.3, shock absorber design;

[0016] S3. Design of liftable rear suspension structure for amphibious vehicle;

[0017] S3.1. Design of lifting mechanism of amphibious vehicle's liftable suspension;

[0018] S3.2. Selection and design of components for the liftable suspension system of an amphibious vehicle.

[0019] Furthermore, the calculation and verification of the motor of the amphibious vehicle includes the following:

[0020] (1) Preliminary selection of motor model;

[0021] (2) Overload check of the motor;

[0022] (3) Check the heating of the motor.

[0023] Furthermore, the calculation of the size of the worm includes the following steps:

[0024] (1) Design for contact fatigue strength;

[0025] (2) Calculate the torque T2 acting on the worm gear;

[0026] (3) Determine the elastic influence coefficient

[0027] (4) Determine the contact coefficient Z p ;

[0028] (5) Constant contact stress [σ H ];

[0029] (6) Setting of main parameters of worm gear.

[0030] Furthermore, the parameter selection of the shock absorbing spring includes the following steps:

[0031] (1) Selection of natural frequency;

[0032] (2) Selection of suspension stiffness;

[0033] (3) Selection of suspension static deflection;

[0034] (4) Selection of suspension dynamic deflection;

[0035] (5) Feasibility test of lifting system.

[0036] Furthermore, the design calculation of the elastic element includes the following steps:

[0037] (1) Selection of spring median diameter, wire diameter, and structural form;

[0038] (2) Select the number of spring coils.

[0039] Furthermore, the shock absorber design includes shock absorber size determination:

[0040] The working diameter D of the shock absorber is calculated based on the maximum unloading force F0 of the extension stroke as follows:

[0041]

[0042] Where [P] is the maximum allowable pressure of the working cylinder, which is 3 to 4 MPa; λ is the ratio of the connecting rod diameter to the cylinder diameter, and the double-tube shock absorber takes λ=0.40 to 0.50, and the single-tube shock absorber takes λ=0.30 to 0.35.

[0043] Furthermore, the selection and design of the components of the amphibious vehicle's liftable suspension system include the following:

[0044] (1) Selection and design of tire wheels;

[0045] (2) Selection of brake;

[0046] (3) Design of automobile flange;

[0047] (4) Design of the boom;

[0048] (5) Parameter determination and design of upper and lower double wishbones;

[0049] (6) Design of universal joint transmission device.

[0050] Compared with the prior art, the present invention has the following beneficial effects:

[0051] 1) Enhance the application value of amphibious vehicles. By improving the suspension mechanical structure design, amphibious vehicles can better adapt to different terrains and water environments, have higher driving performance, handling stability and passability, thereby expanding their application areas and mission execution capabilities.

[0052] 2) Promote the development of special vehicle technology. As a type of special vehicle, the improvement of the performance and function of amphibious vehicles is of great significance to the development of special vehicle technology. The suspension mechanical structure design method and theoretical guidance proposed in this study can provide reference for the suspension system design of other special vehicles.

[0053] 3) Promote the progress of engineering practice. This study will verify the feasibility and effectiveness of the design through detailed simulation and experimental verification. The research results will provide practical guidance and technical support for the suspension mechanical structure design of amphibious vehicles, and provide reference and reference for the progress of engineering practice. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 It is a schematic diagram of the force distribution of the double fork arm in the present invention; DETAILED DESCRIPTION

[0055] The following will describe the implementation methods of the present application in detail with the help of accompanying drawings and examples, so that the implementation process of how the present application uses technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0056] The present invention provides a design method for a liftable rear suspension system of an amphibious vehicle, comprising the following steps:

[0057] S1. Calculation of transmission mechanism parameters of the liftable rear suspension;

[0058] S1.1、Calculation and verification of electric motors for amphibious vehicles;

[0059] S1.2, Calculation of worm dimensions;

[0060] S2. Design and parameter selection of shock absorber:

[0061] S2.1, parameter selection of shock absorbing spring;

[0062] S2.2, design calculation of elastic elements;

[0063] S2.3, shock absorber design;

[0064] S3. Design of liftable rear suspension structure for amphibious vehicle;

[0065] S3.1. Design of lifting mechanism of amphibious vehicle's liftable suspension;

[0066] S3.2. Selection and design of components for the liftable suspension system of an amphibious vehicle.

[0067] The details are as follows:

[0068] Calculation of transmission mechanism parameters of liftable rear suspension

[0069] Calculation and verification of electric motors for amphibious vehicles

[0070] 1) Preliminary selection of motor model

[0071] First, the steady-state average power should be calculated. For different working mechanisms, the steady-state average power can be calculated according to the load and speed using the following formula. For this mechanism:

[0072]

[0073] Where P s ——Steady-state average power of the motor (kW);

[0074] G——average coefficient of steady-state load, G=0.8;

[0075] F Q ——Rated load, F Q=8000N; According to the motor's need to drive the suspension spring and tire hub to rotate, the required load needs to be greater than their total mass;

[0076] v n ——average speed, v n =0.17m / s;

[0077] η——total mechanical efficiency, take η=0.85.

[0078] Right now,

[0079] Therefore, the initial selection is the ZD31-4 model motor with a rated power of P n =1.5kW.

[0080] 2) Motor overload check

[0081] The overload check formula of the motor is:

[0082]

[0083] Where P n ——Rated power of the motor at the reference power-on duration (kW);

[0084] F Q ——Rated load, F Q =8000N;

[0085] v n ——average speed, v n =0.17m / s;

[0086] η——Total mechanical efficiency, take η=0.85;

[0087] λ m ——The allowable overload multiple of the motor torque at the base power-on duration is λ m =2.1;

[0088] H is the coefficient that takes into account factors such as voltage drop and maximum torque error, and H=2.2.

[0089] Right now

[0090] The initially selected motor cannot meet the requirements, so the motor selected is ZD32-4, with a rated power of P n =1.7kW.

[0091] 3) Motor heating check

[0092] Assuming the motor has a service life of 15 years, works 20 days a year, 10 times a day, and two shifts of five minutes each time, the expected life of the motor is L'h =15×20×0.8h=240h.

[0093] When checking the heating of the motor, first calculate the required power-on duration ε of the motor according to the following formula:

[0094]

[0095] Where ε is the power-on duration required for the motor;

[0096] P s ——Calculated steady-state average power, P s =1.28kW;

[0097] P n ——Rated power of the motor at the reference power-on duration, P n =1.7KW;

[0098] t——the time of a working cycle, t=30s;

[0099] t w ——The actual working time of the motor in one working cycle,

[0100] Right now

[0101] Therefore, the requirements are met.

[0102] Calculation of worm gear dimensions

[0103] After the output torque of the lifting chassis, the rigidity requirement is relatively low. Therefore, when designing the worm, 45# steel can be selected, and the tooth surface is quenched to a hardness of 45-55HRC.

[0104] 1) Design based on contact fatigue strength:

[0105]

[0106] 2) Torque T2 acting on the worm gear

[0107] According to Z1=2,η=0.8

[0108] T2=9.55×10 6 ×p2 / n2=9.55×10 6 ×0.7×0.2 / 62=215645N·mm(3-8)

[0109] Determine the load factor K, take K A =1.15K β =1K v =1.05

[0110] So K=K A ×K β ×K v =1.15×1×1.05=1.21

[0111] 3) Determine the elastic influence coefficient (Cast tin bronze worm wheel matches steel worm)

[0112] 4) Determine the contact coefficient Z p

[0113] Assumptions From the table, we can find Z p =2.9

[0114] 5) Determine the contact stress [σ H ]

[0115] According to the material ZCuSn10P1, the hardness of the worm helical tooth surface is >45HRC, and the allowable stress of the worm wheel [σ H ]'=268MPa

[0116] N=60j n2 L h =60×1×62×46720=1.74×10 8 (3-9)

[0117] Life Coefficient Then [σ H ]=K HN ×[σ H ]'=0.67×268=179.56MPa

[0118] Calculate the center distance:

[0119]

[0120] Take a=100, because i-15 takes the modulus m=5, d1=50mm.

[0121] At this time The contact coefficient Zρ'=2.6<2.9, so the calculation result is available.

[0122] 6) Main parameters of worm gear

[0123] The axial pitch of the worm gear Pa = 15.7, and the diameter coefficient q = 10, the diameter of the tooth top circle d a1 =60, tooth root circle d f1 =38, pitch circle lead angle r=11°, worm axial tooth thickness Sa=5π / 2=7.85mm.

[0124] 7) Turbine

[0125] Number of teeth Z2=31

[0126] Pitch circle diameter d = m × Z2 = 155 mm

[0127] Root diameter = 165mm.

[0128] Design and parameter selection of shock absorber

[0129] Parameter selection of shock absorbing spring

[0130] Self-oscillation frequency:

[0131] The natural frequency of the vibration system composed of the front and rear suspensions and their sprung masses is one of the main parameters affecting the ride comfort of the car. Since the mass distribution coefficient ε of modern cars is approximately equal to 1, there is no connection between the vibrations of the two points on the front and rear axles of the car body.

[0132] Different vehicles have different requirements for ride comfort. Passenger vehicles that are mainly used to transport people have the highest requirements for ride comfort, followed by buses and trucks. For passenger vehicles with an engine displacement of less than 1.6L, the full-load bias frequency of the front suspension is required to be 1.00-1.45Hz, and the rear suspension is required to be 1.17-1.58Hz. In principle, the larger the engine displacement of a passenger car, the smaller the bias frequency of the suspension should be. The full-load front suspension bias frequency is required to be 0.80-1.15Hz, and the rear suspension is required to be 0.98-1.30Hz. When a truck is fully loaded, the front suspension bias frequency is required to be 1.50-2.10Hz, and the rear suspension is required to be 1.70-2.17Hz. The smaller the bias frequency, the better the ride comfort. After selecting the bias frequency, the static deflection of the suspension can be calculated.

[0133] The rear suspension offset frequency selected in this embodiment is: n=1.1.

[0134] Suspension stiffness

[0135] According to the suspension stiffness formula:

[0136] K=(2πn) 2 m (4-1)

[0137] Where:

[0138] m——sprung mass

[0139] K——Angular stiffness of the suspension

[0140] n——the bias frequency of the suspension,

[0141] Rear wheel sprung mass:

[0142]

[0143] Theoretical stiffness of rear suspension:

[0144] K 后 =(2πn2) 2 m 后 =(2π×1.1) 2 ×1051.2=50163.8N / mm (4-4)

[0145] l=350mm a=200mm α=10° (4-5)

[0146] Actual stiffness of the rear suspension:

[0147]

[0148] Suspension static deflection

[0149] Static deflection of suspension f c It refers to the load F on the suspension when the car is fully loaded and stationary. w The ratio of the suspension stiffness c at this time, that is, f c =F w / c, when a suspension with linearly changing elastic characteristics is used, the static deflection of the rear suspension can be expressed as:

[0150] f c =mg / K, where: g——acceleration due to gravity

[0151] Static deflection of rear suspension:

[0152] f 后 =m 后 g / K 后 =1051.2×9810÷50163.8=205.6mm (4-7)

[0153] Suspension dynamic deflection

[0154] Dynamic deflection of suspension f d It refers to the vertical displacement of the wheel center relative to the frame (or body) when the suspension is compressed from the fully loaded static equilibrium position to the maximum deformation allowed by the structure. In order to prevent the car from frequently hitting the limit block during driving, the suspension should have sufficient dynamic deflection. d / f c The value should be no less than 0.5, for buses it should be no less than 0.75, for trucks it should be 1.0, and for off-road vehicles driving on harsh road conditions, the value should be even larger.

[0155] I design the suspension for off-road vehicles, so d / f c The value should be no less than 0.5.

[0156] Dynamic deflection of rear suspension:

[0157] f d≥0.5f c =0.5×205.6=102.8mm (4-8)

[0158] Therefore, the dynamic deflection of the rear suspension is 120mm.

[0159] Design calculation of elastic elements

[0160] Spring middle diameter, wire diameter, and structure:

[0161] The maximum working load F1 of the suspension on one side is obtained by the following formula:

[0162]

[0163] The minimum working load F2 of the suspension on one side is obtained by the following formula:

[0164]

[0165] The spring index (winding ratio) is C=6.

[0166] The curvature coefficient K' is obtained by the following formula:

[0167]

[0168] Steel wire tensile strength limit σ B =1200MPa

[0169] The allowable stress [τ] is then given by:

[0170] [τ]=0.5σ B =0.5×1200=600MPa (4-12)

[0171] The spring wire diameter d is given by the following formula:

[0172]

[0173] The spring center diameter D2 can be obtained from the following formula:

[0174] D2=Cd=6×13=78mm (4-14)

[0175] Calculate the spring stiffness K 弹 :

[0176]

[0177] The structural form used in this spring design is coil spring.

[0178] Number of spring coils

[0179] The number of working cycles is z=6

[0180] The total number of spring turns Z1 is obtained from the following formula:

[0181] Z1=Z+2=6+2=8 (4-16)

[0182] The spring pitch P is given by:

[0183]

[0184] The gap between the two circles δ is obtained from the following formula:

[0185] δ=Pd=26-13=13mm (4-18)The free height of the spring is obtained from the following formula:

[0186] H0=PZ1+1.5d=26×8+1.5×13=227.5mm (4-19)

[0187] Shock absorber design

[0188] Main dimensions of shock absorber:

[0189] The working diameter D of the shock absorber is calculated based on the maximum unloading force F0 of the extension stroke as follows:

[0190]

[0191] Where [P] is the maximum allowable pressure of the working cylinder, which is 3 to 4 MPa; λ is the ratio of the connecting rod diameter to the cylinder diameter, and the double-tube shock absorber takes λ=0.40 to 0.50, and the single-tube shock absorber takes λ=0.30 to 0.35.

[0192] The working cylinder diameter D of the shock absorber is 20mm, 30mm, 40mm, (45mm), 50mm, 65mm, etc. The selection should be made according to the standard.

[0193] In this design, [P]=3, λ=0.5.

[0194] The diameter of the rear suspension shock absorber working cylinder is obtained by the following formula:

[0195]

[0196] Oil cylinder diameter Dc;

[0197] Oil storage tank diameter The wall thickness is 2mm and the material can be 20 steel.

[0198] Rear oil tank diameter D C后 It is derived from the following formula:

[0199] D C后 =1.4D=1.4×40=56mm (4-21).

[0200] Design of lifting mechanism of amphibious vehicle's liftable suspension:

[0201] The movement of an amphibious vehicle on land is no different from that of an ordinary vehicle, but when sailing in water, it is greatly affected by the hydrodynamic environment. For example, if there is a requirement for sailing speed, since amphibious vehicles are blunt-body structures with poor streamlines, resulting in large water resistance, it is necessary to consider the vehicle shape design to reduce water resistance and use efficient propulsion equipment to achieve the speed requirement. In addition, the harsh marine environment places higher requirements on the stability and wave resistance of amphibious vehicles

[15] . The lifting mechanism of the rear suspension of an amphibious vehicle is mainly composed of a motor, a motor seat, a worm, a turbine, a bearing, a bearing seat, a coupling, a shock absorber, an upper and lower swing arm, a brake, and the like.

[0202] Modeling and analysis of the liftable suspension parts of an amphibious vehicle

[0203] Modeling of tire hub: Tire is a ring-shaped rubber product, which is usually installed on the rim of the vehicle to support the vehicle body, buffer external impact, achieve contact with the road surface, and ensure the driving performance of the vehicle. The tire model used in this design is 275 / 45R21, with a section width of 275mm, a section height of 275x0.45=123.75, and a tire outer diameter of 21x25.4+2x123.75=780.9mm. The inner diameter of the tire (and the wheel hub diameter) is 21x25.4=533.4mm.

[0204] Modeling of brakes: Automobile brakes are the braking devices of automobiles. They are components that generate forces (braking forces) that hinder the movement or movement trend of vehicles, allowing vehicles to slow down or stop. They are important components for safe driving of automobiles. Brakes used in automobiles are almost all friction type, which can be divided into drum type and disc type. This design uses disc brakes. Because disc brakes have fast heat dissipation, light weight, simple structure, easy adjustment, good high temperature resistance under load, and stable braking effect.

[0205] Modeling of automobile flange: Automobile flange is a disc-shaped metal part, usually with fixing holes, used to connect wheels or other parts. Its main function is to connect wheels. It can also improve driving stability, reduce the risk of rollover, and increase the limit of control. It can accurately locate the center of the wheel and the half shaft, transmit power, and facilitate the fixing of the brake disc and the removal of the wheel.

[0206] Modeling of the articulated arm: The articulated arm, also known as the "ram's horn", is one of the important parts of the steering axle of the car. It can make the car run smoothly and the transmission direction is sensitive. When the vehicle is running, it plays the role of bearing various impact loads, so it is required to have high strength.

[0207] Parameter determination and modeling diagram of upper and lower double wishbones: Double wishbone is also called double A-arm suspension or double rocker arm suspension, which is a type of double wishbone suspension. Double wishbone suspension is composed of two A-arms of different lengths and shock absorbers acting as pillars. The lateral force is absorbed by both wishbones at the same time, and the pillars only bear the weight of the vehicle body, so the lateral stiffness is large. The advantage of double wishbone suspension is that it can provide better suspension performance and handling. Compared with other suspension systems, double wishbone suspension has better lateral stiffness, can better absorb the impact caused by uneven road surface, and improve the stability and handling of the vehicle. In addition, the structure of double wishbone suspension is relatively simple, easy to install and maintain, and relatively low cost.

[0208] In order to allow the tire to be lifted to a height of more than 250mm, the double wishbone designed this time is 360mm long and 15mm thick. Based on the McPherson suspension design, its stress conditions are analyzed. Figure 1 The force distribution.

[0209] Modeling of universal joint transmission device: The ball cage universal joint is usually composed of an inner sleeve, an outer sleeve, a ball cage and balls. The ball cage universal joint is a constant velocity universal joint. The universal joint is a universal joint, which is a component that can change the angle of power transmission. It is used to change the direction of the transmission axis. It is the "joint" component of the universal transmission device of the automobile drive system. The maximum angle between the two axes of the ball cage universal joint is between 42 and 47 degrees. This design uses a ball cage universal joint because the deflection angle is large enough to meet the lifting height of more than 250mm, so the angle of this design is 46°.

[0210] Modeling of shock absorber: The double-acting copper shock absorber is mainly composed of spring, main cylinder, inner cylinder, axial piston, seal and air pressure chamber.

[0211] Modeling of worm gear: Worm gear is a mechanical transmission device consisting of a worm and a worm wheel. Worm gear is usually used for motion and power transmission between staggered axes, where the staggered angle of the two axes is usually 90°. The worm has one or more helical teeth that mesh with the teeth of the worm wheel to form a gear pair. This design makes the worm gear have the characteristics of compact structure, smooth transmission and large transmission ratio.

[0212] Connection between the worm gear and the body: The worm gear and the body are tightened together by bolts and nuts.

[0213] In summary, the above are only preferred embodiments of the present invention and are not intended to limit the present invention in any form. Any simple modifications or equivalent changes made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the present invention.

[0214] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any simple modification, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are within the scope of the technical solution of the present invention.

Claims

1. A design method for a liftable rear suspension system for an amphibious vehicle, characterized in that: The steps include: S1. Calculation of transmission mechanism parameters of the liftable rear suspension; S1.1、Calculation and verification of electric motors for amphibious vehicles; S1.2, Calculation of worm dimensions; S2. Design and parameter selection of shock absorber: S2.1, parameter selection of shock absorbing spring; S2.2, design calculation of elastic elements; S2.3, shock absorber design; S3. Design of liftable rear suspension structure for amphibious vehicle; S3.

1. Design of lifting mechanism of amphibious vehicle's liftable suspension; S3.

2. Selection and design of components for the liftable suspension system of an amphibious vehicle.

2. The design method of the amphibious vehicle liftable rear suspension system according to claim 1 is characterized in that: The calculation and verification of the motor of the amphibious vehicle includes the following: (1) Preliminary selection of motor model; (2) Overload check of the motor; (3) Check the heating of the motor.

3. The design method of the amphibious vehicle liftable rear suspension system according to claim 1, characterized in that: The worm size calculation includes the following steps: (1) Design for contact fatigue strength; (2) Calculate the torque T2 acting on the worm gear; (3) Determine the elastic influence coefficient (4) Determine the contact coefficient Z p ; (5) Constant contact stress [σ H ]; (6) Setting of main parameters of worm and worm gear.

4. The design method of the amphibious vehicle liftable rear suspension system according to claim 1, characterized in that: The parameter selection of the shock absorbing spring comprises the following steps: (1) Selection of natural frequency; (2) Selection of suspension stiffness; (3) Selection of suspension static deflection; (4) Selection of suspension dynamic deflection.

5. The design method of the amphibious vehicle liftable rear suspension system according to claim 1, characterized in that: The design calculation of the elastic element includes the following steps: (1) Selection of spring median diameter, wire diameter, and structural form; (2) Select the number of spring coils.

6. The design method of the amphibious vehicle liftable rear suspension system according to claim 1, characterized in that: The shock absorber design includes shock absorber sizing: The working diameter D of the shock absorber is calculated based on the maximum unloading force F0 of the extension stroke as follows: Where [P] is the maximum allowable pressure of the working cylinder, which is 3 to 4 MPa; λ is the ratio of the connecting rod diameter to the cylinder diameter, and the double-tube shock absorber takes λ=0.40 to 0.50, and the single-tube shock absorber takes λ=0.30 to 0.

35.

7. The design method of the amphibious vehicle liftable rear suspension system according to claim 1, characterized in that: The selection and design of the parts of the amphibious vehicle liftable suspension system include the following: (1) Selection and design of tire and wheel hubs; (2) Selection of brake; (3) Design of automobile flange; (4) Design of the boom; (5) Parameter determination and design of upper and lower double wishbones; (6) Design of universal joint transmission device.

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