Design method of active suspension omni-directional robot chassis assembly

Abstract

The invention relates to the technical field of chassis of active suspension omni-directional robots, in particular to a design method of a chassis assembly of an active suspension omni-directional robot, which comprises the following steps: S1, chassis frame design; s2, designing an AGV wheel set; s3, control design of active suspension; s4, designing a control system; s5, designing a power supply system; s6, designing a driving system; the stable, flexible and efficient suspension system is designed to improve the performance of the robot in a special application scene, the suspension system has self-adaptability, high stability and high movement efficiency, the height of the chassis can be automatically adjusted under different terrain conditions, the stability of the robot is kept, and the application range of the robot is widened. And the moving range and flexibility of the robot are improved.

Description

Technical Field

[0001] The invention relates to the technical field of chassis of an active suspension omnidirectional robot, and in particular to a design method of a chassis assembly of an active suspension omnidirectional robot. Background Art

[0002] With the rapid development of technologies such as artificial intelligence, computer vision, and machine learning, the application of robots in various fields continues to expand, and the requirements for robot chassis are becoming more and more stringent. Especially in some complex application scenarios, such as uneven terrain and harsh environments, the performance, stability, and reliability of robot chassis face severe challenges. In order to meet the needs of different application scenarios, the research and development of robot chassis is constantly advancing towards higher performance and more personalized directions.

[0003] Active suspension system refers to a suspension system that can adjust parameters such as height, spring stiffness and damping in real time according to ground conditions and chassis status. This technology can improve the mobility of mobile chassis in complex terrain and increase stability and reliability. Active suspension system was originally used in automobiles. The world's first vehicle with active suspension system was Toyota Soarer, which used the world's first semi-active suspension system - TEMS (Toyota Electronic Modulated Suspension). At that time, this system only had two adjustment levels of "soft" and "hard". In the 1990s, this system was updated to three adjustment levels, which can respond to more driving conditions. However, this system is semi-active, and only the shock absorber damping is adjusted, and the height of the vehicle body cannot be adjusted. Later, with the development of technology, the active suspension system was gradually miniaturized and applied to the robot frame. However, since the application of robots is in the early stages of development, most mobile robots still use passive suspension design, and semi-active or active suspension design is less used.

[0004] Therefore, a design method for an active suspension omnidirectional robot chassis assembly is proposed to solve the above problems. Summary of the invention

[0005] The purpose of the present invention is to provide a design method for an active suspension omnidirectional robot chassis assembly in order to solve the above-mentioned problems, aiming to study a mobile chassis with an active suspension system and design a stable, flexible and efficient suspension system to improve the performance of the robot in special application scenarios.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions, a design method of an active suspension omnidirectional robot chassis assembly, comprising the following steps:

[0007] S1, chassis frame design;

[0008] S2, AGV wheel design;

[0009] S3, active suspension control design;

[0010] S4. Control system design;

[0011] S5. Power system design;

[0012] S6. Drive system design.

[0013] Preferably, the chassis frame design in step S1 includes the following steps:

[0014] S1.1. The triangular main frame is composed of three large-diameter thin-walled aluminum square tubes. Plates and resin light-cured printed parts are embedded inside the aluminum square. The printed parts are printed with high-precision SLA light-cured resin, which ensures accuracy and good mechanical properties. The printed parts are equipped with hexagonal holes that can be embedded with self-locking nuts to achieve one-way installation;

[0015] S1.2. After the main frame is built, the finite element stress analysis is performed on the aluminum square. According to the maximum stress of the vehicle body, the maximum stress is 1.989×10 7 N / m 2 , concentrated in the middle part.

[0016] Preferably, the AGV wheel set design in step S2 includes the following steps:

[0017] S2.1. Design of driving wheel set: In the design, a brushless motor is selected as the driving wheel set design, and a D-hole clamping coupling is selected as the coupling;

[0018] S2.2. Heading axis system design: In the design, a brushless DC motor is selected as the driving force source of the heading part, the transmission mechanism adopts shaft transmission, and the heading axis system uses cross roller bearings.

[0019] Preferably, the outer layer material of the rubber-coated wheel in the driving wheel set is polyurethane with a hardness of 55a.

[0020] Preferably, in the control design of the active suspension in step S3, the active suspension can adjust some parameters in real time according to the road conditions, such as the height of the chassis relative to the ground, the damping rebound rate, and the hardness of the suspension (K value). For flat roads, the active suspension system can reduce the contact area between the chassis and the road surface. When the system is powered off, it is necessary to ensure that the vehicle body has a basic supporting force so that the vehicle body chassis does not contact the ground. Therefore, the active suspension system needs to have a certain supporting force even when the power is off. There are two options for the design of the mechanism here: mechanical limit or low K value spring, and the parameters of the spring are designed as follows:

[0021] According to the chassis weight of the vehicle, and then according to the gravity calculation formula

[0022] G=mg (3-1)

[0023] The gravity value of the vehicle body is obtained. Since the vehicle body is a three-steering wheel mechanism with three contact points with the ground, the force value of each supporting wheel group and the stroke value of the shock absorber with installed spring are obtained.

[0024] Under this condition, the spring k value is designed. The k value design formula is as follows:

[0025]

[0026] Where: G represents the rigidity modulus corresponding to the spring material, d represents the wire diameter, D m Represents the spring outer diameter D o Subtract wire diameter d; N c Represents the effective number of coils, which is the total number of coils of the spring minus 2.

[0027] Preferably, in the control design of the active suspension in step S3, when there is an initial amount (shock absorber) and the electric active suspension on the chassis starts to work, the additional damping and supporting force mechanism is designed, taking into account the space utilization and mechanism execution efficiency, and a gear rack driven by a brushless motor is used to provide it. In principle, the gear rack mechanism driven by the FOC motor can generate additional different torques and damping under different working modes of the driving motor and different PID values, thereby changing the height and hardness of the suspension. According to the torque transmission formula:

[0028] F=M / L (3-3)

[0029] In the process of converting torque into supporting force, it is divided by the force transmission distance. The smaller the distance, the greater the equivalent supporting force obtained, and the smaller the outer diameter of the gear parameter should be, the better.

[0030] Preferably, in the control design of the active suspension in step S3, it is not appropriate to change the height simply by means of a gear rack because of the existence of the shock absorber. This is because when the chassis is lifted, if the fixing point of the shock absorber remains unchanged, the wheel set is lifted relative to the chassis, and the compression of the shock absorber is reduced, and the motor output torque is greater. When the vehicle body is lifted to the highest point, the shock absorber returns to its original length, and the RoboMaster M2006 alone cannot support the vehicle body. Therefore, the shock absorber mechanism needs to be lifted together to achieve the lifting of the entire mechanism. In order to achieve self-locking at different heights, a trapezoidal screw mechanism is selected, and the lead selection is calculated based on the height that the active suspension can be raised and the peak speed of the driving motor. The screw is selected for compatibility, and a calculation and verification analysis is performed on it. The screw mechanism is verified as follows:

[0031] According to the parameters of the trapezoidal screw, determine the outer diameter d, pitch p, middle diameter d2, and tooth angle α of the screw;

[0032] According to the lead L value, the formula for calculating the number of lines of the screw is as follows

[0033] n=L / p (3-4)

[0034] Calculate the number of threads n of the screw and the helix angle β:

[0035] β=arctan(L / πd2) (3-5)

[0036] The β value is obtained.

[0037] According to the material properties of 304 stainless steel, the allowable stress σ value and the allowable shear stress τ value of the screw are determined.

[0038] According to the static load F value, the axial stress σ1 of the screw is calculated as

[0039] σ1=F / π(d2-2) / 4 (3-6)

[0040] The calculated σ1 value is less than the allowable stress σ. Axial stress refers to the compressive or tensile stress in the axial direction of the screw, which is used to check whether the screw is buckled or broken.

[0041] According to the static load F value, the shear stress τ1 formula of the screw is calculated

[0042]

[0043] The τ1 value obtained is less than the allowable shear stress τ.

[0044] The beneficial effects of the present invention are as follows: the present invention designs a stable, flexible and efficient suspension system to improve the performance of the robot in special application scenarios. The suspension system has adaptability, high stability and high motion efficiency, and can automatically adjust the chassis height under different terrain conditions, maintain the stability of the robot, and improve the robot's range of motion and flexibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a schematic diagram of the influence of rib arrangement on the stiffness of the closed box structure in the present invention;

[0046] Figure 2 This is a diagram of the embedded printed part of the aluminum square tube in the present invention;

[0047] Figure 3 It is the main triangular framework diagram of the present invention;

[0048] Figure 4 It is an exploded view of the drive wheel shaft assembly in the present invention. DETAILED DESCRIPTION

[0049] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0050] A design method for an active suspension omnidirectional robot chassis assembly is described below with a specific embodiment:

[0051] The whole includes:

[0052] (1) Suspension system: The active suspension chassis needs to be equipped with a suspension system, including sensors, suspension brackets, shock absorbers and other components. Among them, the sensor can sense changes in terrain, the suspension bracket can support the weight of the robot, and the screw drive system can control the suspension height and hardness.

[0053] (2) Drive system: The active suspension chassis needs to be equipped with a drive system, including components such as motors, reducers, and steering systems. The motor can provide power, the reducer can reduce the speed of the motor output, and the steering system can control the steering of the robot.

[0054] (3) Chassis structure: The active suspension chassis needs to have a reasonable structural design, including components such as chassis frame, wheels and suspension brackets. Among them, the chassis frame needs to have sufficient strength and rigidity, the wheels need to have good wear resistance and grip, and the suspension bracket needs to have reasonable support and adjustment functions.

[0055] (4) Control system: The active suspension chassis needs to be equipped with a control system, including sensors, controllers, actuators and other components. Among them, the sensor can sense the robot's state and environmental changes, the controller can make control decisions based on the sensor's feedback, and the actuator can control the chassis' movement and suspension height, etc.

[0056] (5) Power system: The active suspension chassis needs to be equipped with a power system, including batteries, chargers and other components. The battery needs to have sufficient power and capacity to meet the needs of the robot's work, and the charger needs to have a suitable charging speed and safety protection measures.

[0057] The specific performance indicators of active suspension chassis design are as follows:

[0058] (1) Terrain adaptability: The chassis needs to be able to adapt to various terrains, including uniform roads, uneven roads, slopes, sandy roads, gravel roads, etc.

[0059] (2) Motion stability: The chassis needs to maintain a stable motion state to ensure precise control of the robot and efficient execution of tasks.

[0060] (3) Maneuverability: The chassis needs to have excellent maneuverability, including quick steering, flexible turning, and rapid acceleration, in order to adapt to complex mission environments.

[0061] (4) Load capacity: The chassis needs to have sufficient load capacity to meet the needs of various tasks of the robot.

[0062] (5) Safety: The chassis needs to be safe and reliable, including avoiding accidents such as rollover and collision.

[0063] (6) Energy efficiency: The chassis needs to have efficient energy utilization capabilities to extend the robot's working time.

[0064] (7) Control accuracy: The chassis needs to have high-precision control capabilities to ensure accurate navigation and motion control of the robot.

[0065] (8) Adaptability: The chassis needs to be able to adapt and make corresponding adjustments and responses based on different mission requirements and environmental changes.

[0066] (9) Fault diagnosis and maintainability: The chassis needs to have fault diagnosis and maintainability to facilitate the maintenance and upkeep of the robot.

[0067] (10) Cost-effectiveness: The chassis needs to be cost-effective, that is, the cost must be reasonably controlled while meeting all the above performance indicators.

[0068] Chassis frame design

[0069] The main frame of the robot chassis is one of the key designs, and the design of the chassis frame mainly depends on the driving wheel set and development requirements. In the design of the robot wheel set, two steering wheels, three steering wheels or four steering wheels can be used. When selecting the number of steering wheels, it is necessary to comprehensively consider factors such as the robot's application scenarios, task requirements, and performance requirements. Compared with the two-steering-wheel and four-steering-wheel solutions, the three-steering-wheel solution has the advantages of a smaller turning radius, higher stability, and lower driving cost. Taking the above factors into consideration, the three-steering-wheel solution has certain advantages in the design of the robot wheel set and is suitable for some application scenarios that require a small turning radius and higher stability. Therefore, this design uses three large-diameter thin-walled aluminum square tubes to form a triangular main frame to adapt to the placement and connection of the three-steering-wheel wheel set. The design parameters and details are as follows:

[0070] The aluminum square tube is made of 6061 aluminum alloy and is processed and manufactured using laser cutting. The surface oxidation treatment of the aluminum square is beneficial to prevent rust caused by long-term work. The length and width of the square tube are 40mm*40mm, and the thickness is 1mm. The large-diameter thin-walled tube can more effectively withstand the bending moment when working under stress. At the same time, the internal space can be used for wiring and installation of other components, making the chassis more integrated, such as Figure 1 This is the aluminum square reinforcement solution table. After considering the weight and processing difficulty, the idea of ​​embedding printed parts in the aluminum square is chosen. Compared with the multi-rib type in the chart, the price and processing are more suitable.

[0071] like Figure 2 As shown, the aluminum square tube is embedded with plates and resin light-curing printed parts. The printed parts are printed with high-precision SLA light-curing resin, which ensures accuracy and good mechanical properties. The printed parts are equipped with hexagonal holes that can be embedded with self-locking nuts to achieve one-way installation, making assembly faster and more convenient.

[0072] The main frame is connected by three aluminum square tubes and stacked plates. Compared with welding, it is easier to disassemble and maintain, and the strength is also guaranteed. A rotating base can be installed in the middle part to facilitate the construction of a development platform for multi-purpose design and research, such as Figure 3 It is a single-piece main frame.

[0073] After the main frame is built, the finite element stress analysis is performed on the aluminum square. According to the maximum stress of the car body, the maximum stress is 1.989×10 7 N / m 2 , concentrated in the middle part.

[0074] AGV wheel design

[0075] Drive wheel design

[0076] The driving wheel set is an important part of the active suspension chassis design. In this part, the motor and reducer are the core components, which are responsible for providing enough driving force and torque so that the robot can travel and turn.

[0077] When selecting a motor, the considerations for brushless and brushed motors are as follows:

[0078] Table 1 Comparison of brushed motor and brushless motor structure and parameters

[0079]

[0080]

[0081] According to the above selection comparison, a brushless motor is selected as the drive wheel set design. The motor model is the RoboMaster M3508 DC brushless motor developed by DJI. This motor amplifies the torque output through a planetary gear reducer, with a reduction ratio of 1:19.203, and the output torque can reach 3N / m. This motor not only has high output power and torque, but also has the advantages of long life and high efficiency, and is suitable for use in the field of robots. The motor and the drive wheel set are connected through a 6061 aluminum alloy motor seat, which can effectively unload the load during work and reduce mechanical damage caused by vibration and collision.

[0082] In terms of couplings, this design uses a D-hole clamping coupling, which can transmit torque more effectively than traditional clamping couplings and prevent power loss caused by slippage. This coupling can ensure effective connection between the output shaft and the rubber-coated wheel and prevent mechanical damage.

[0083] The rubber-coated wheel is another important component of the driving wheel set. This embodiment selects a rubber-coated wheel with a diameter of 120 mm. The outer layer material is polyurethane with a hardness of 55a. The robot can pass normally in most terrains. At the same time, the reasonable hardness of the rubber coating ensures the effective friction between the driving wheel and the ground, preventing the vehicle body from slipping due to insufficient friction during rapid start-up. The reasonable hardness can also reduce the probability of dust contamination during operation and increase the service life of the wheel set. This wheel hub has the characteristics of good wear resistance and strong pressure resistance, and has shown excellent performance in practical applications.

[0084] Drive shaft design Figure 4 shown.

[0085] Heading axis design

[0086] The design of the heading part is crucial, as it is the core part of the robot's steering and navigation. In the design, the RoboMaster 6020 DC brushless motor was selected as the driving force source of the heading part. This motor is a high-performance DC brushless motor with an internal integrated driver, with a maximum torque of 1.25N·m. The hollow design allows the conductive slip ring to connect the drive wheel group electrical wiring, and the power of the motor is transmitted to the heading axis system through the transmission shaft.

[0087] In order to ensure the working stability and reliability of the heading part, the transmission mechanism adopts shaft drive. At present, there are three ways to drive the heading direction of the steering wheel, namely inverted direct drive, gear drive and shaft drive. Compared with inverted direct drive and gear drive motor, many fixing mechanisms can be omitted, which can reduce more weight. At the same time, the transmission shaft is made of 6061 aluminum alloy, which can efficiently meet the transmission requirements in terms of strength and space utilization. The middle part of the shaft is left empty to facilitate the use of conductive slip rings to power the drive mechanism, thereby reducing the weight and volume of the entire robot.

[0088] The heading axis system uses RA9800 crossed roller bearings, which are high-precision, high-rigidity rolling bearings that are widely used in many high-speed, high-load applications. Crossed roller bearings use rolling elements that are alternately arranged on the inner and outer rings, making their load-bearing capacity much greater than other rolling bearings of the same size. In addition, the bearing has a large number of rolling elements inside, low rolling friction, and fast speed response, and can maintain stable operation in a high-speed rotation environment. In addition, the design of multiple rolling elements makes it evenly distributed, with low friction and long service life.

[0089] Active suspension design

[0090] During the robot's driving process, the active suspension system can adjust some parameters in real time according to the road conditions, such as the height of the chassis relative to the ground, the damping rebound rate, and the hardness of the suspension (K value). The changes in these parameters can adapt to different road conditions and robot states, thereby improving the robot's driving efficiency and stability.

[0091] For flat roads, the active suspension system can reduce the contact area between the chassis and the road surface, reduce friction resistance, thereby reducing the robot's energy loss and improving the robot's driving efficiency. In addition, the active suspension system can also adjust the suspension height in real time according to the height of the road surface to maintain the distance between the robot chassis and the road surface, thereby improving the robot's stability and accuracy on flat roads.

[0092] However, on uneven roads, the importance of active suspension systems is even more prominent. The active suspension system can quickly adjust the chassis height and suspension stiffness by sensing the height of the road surface in real time to keep the robot chassis in contact with the road surface, thereby ensuring the stability and stability of the robot on uneven roads. In addition, the active suspension system can also adapt and adjust the suspension height in a short time, reducing the bumps when the robot passes through bumps and depressions, and protecting the normal operation of important robot equipment, such as cameras and sensors.

[0093] First, when the system is powered off, it is necessary to ensure that the vehicle body has a basic support force so that the vehicle chassis does not touch the ground. Therefore, the active suspension system needs to have a certain support force even when the power is off. There are two options for the design of the mechanism here: mechanical limit or low K value spring. The parameters of the spring are designed as follows:

[0094] The chassis weight is 11kg, according to the gravity calculation formula

[0095] G=mg (3-1)

[0096] The vehicle body gravity value is 107.8. Since the vehicle body is a three-steering wheel mechanism with three contact points with the ground, the force on each supporting wheel group is 35.9N, and the stroke of the spring-installed shock absorber is about 35mm.

[0097] Under this condition, the spring k value is designed. The k value design formula is as follows:

[0098]

[0099] Where: G represents the rigidity modulus corresponding to the spring material, d represents the wire diameter, D m Represents the spring outer diameter D o Subtract wire diameter d; N c Represents the effective number of coils, which is the total number of coils of the spring minus 2.

[0100] Select the spring material. The G values ​​corresponding to the commonly used spring materials are shown in Table 3-2

[0101] Table 2 Spring rigidity modulus of different materials

[0102] Material Rigidity modulus G{ / 2} Carbon spring steel 79000 Stainless steel 71000 Silicon Bronze Wire 41000 Tin bronze wire 40000

[0103] By comparing the G value and practicality, the material used is carbon spring steel, and the outer diameter of the shock absorber spring is D o It is 17mm, and the wire diameter d is 1.8mm. Considering that the shock absorber travel number of turns is 15 and the effective number of turns is 13, the calculated k value is 2.27, which fully meets the requirements with a safety factor of 1.2.

[0104] When there is an initial amount (shock absorber) and the electric active suspension on the chassis starts to work, the additional damping and support force mechanism is designed, taking into account the space utilization and mechanism execution efficiency, and is provided by a gear rack driven by a brushless motor. In principle, the gear rack mechanism driven by the FOC motor can generate additional different torques and damping under different working modes and different PID values ​​of the drive motor, thereby changing the height and hardness of the suspension. The drive motor uses a RoboMaster M2006 motor with a maximum torque of 1.7N / m, which is matched with a small K value shock absorber to form a cascade system. According to the formula for torque transmission:

[0105] F=M / L (3-3)

[0106] In the process of converting torque into supporting force, it is divided by the force transmission distance. The smaller the distance, the greater the equivalent supporting force obtained, and the smaller the outer diameter of the gear parameter should be, the better.

[0107] The force analysis of the gear rack was verified and simulated according to the working condition of the limit torque of 3N / M. The maximum stress is concentrated at the root of the tooth, which is 4.88×10 7 N / m 2, below the yield strength of 5.51×10 7 N / m 2 , to meet the needs.

[0108] As for the height change, due to the existence of shock absorbers, it is not appropriate to change the height simply by gear racks. Because when the chassis is lifted, if the shock absorber fixing point remains unchanged, the wheel set is lifted relative to the chassis, the shock absorber compression is reduced, and the motor output torque is greater. When the vehicle body is lifted to the highest, the shock absorber returns to its original length. RoboMaster M2006 alone cannot support the vehicle body, so the shock absorber mechanism needs to be lifted together to achieve the lifting of the entire mechanism. In order to achieve self-locking at different heights, a trapezoidal screw mechanism is selected. The screw uses a T8 screw, and the lead selection calculation is as follows: The active suspension can be raised to a height of 65mm. In order to respond quickly, it needs to be completed within 1s. The peak speed of RoboMaster M2006 is 500rpm, that is, 8.3 seconds. According to calculations, the lead needs to be at least about 7.8. For compatibility, a screw with a lead of 12mm is selected, and it is calculated and verified. The screw mechanism is verified as follows:

[0109] According to the parameters of the T8 trapezoidal lead screw, the outer diameter d of the lead screw is determined to be 8 mm, the pitch p is 2 mm, the middle diameter d2 is 6.35 mm, and the tooth angle α is 30°.

[0110] Based on the lead L of 12mm, the formula for calculating the number of lines of the screw is as follows

[0111] n=L / p (3-4)

[0112] The number of threads n of the screw is calculated to be 6. The formula for calculating the helix angle β is:

[0113] β=arctan(L / πd2) (3-5)

[0114] It is obtained that β=63.4°.

[0115] The lead refers to the distance the nut moves when the screw rotates one circle, the number of lines refers to the number of helical lines on the screw, and the helix angle refers to the angle between the tangent of the helix line in the axial plane of the screw and the plane perpendicular to the axis.

[0116] According to the material properties of 304 stainless steel, the allowable stress σ of the screw is determined to be 100MPa, and the allowable shear stress τ is determined to be 60MPa.

[0117] According to the static load F of 50N, the axial stress σ1 of the screw is calculated as follows:

[0118] σ1=F / π(d2-2) / 4 (3-6)

[0119] The calculated value of σ1 is 0.28MPa, which is less than the allowable stress σ. Axial stress refers to the compressive or tensile stress in the axial direction of the screw, which is used to check whether the screw is buckled or broken.

[0120] According to the static load F of 50N, the shear stress τ1 formula of the screw is calculated

[0121]

[0122] The obtained value of τ1 is 0.42MPa, which is less than the allowable shear stress τ. Shear stress refers to the shear stress in the circumferential direction of the screw, which is used to check whether the screw is twisted or worn.

[0123] In summary, the T8 lead screw made of 304 stainless steel with a lead of 12mm is qualified in the static load verification under 50N.

[0124] The heading part of this design is structurally reasonable, stable and reliable, and can provide sufficient power and support for the robot to help it achieve precise steering and navigation during operation. The design of the drive wheel group has an important impact on the performance and stability of the active suspension chassis. By comprehensively optimizing the selection and structural design of each component, a better robot chassis design can be obtained.

[0125] The following table is the overall parameters of the chassis:

[0126] Table 3 Active suspension chassis design vehicle parameters

[0127] Technical indicators parameter Vehicle length (mm) 280 Vehicle width (mm) 220 Vehicle height (mm) 221 Vehicle weight (kg) 8kg

[0128] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A design method for an active suspension omnidirectional robot chassis assembly, characterized in that: The following steps are involved: S1, chassis frame design; S2, AGV wheel design; S3, active suspension control design; S4. Control system design; S5. Power system design; S6. Drive system design.

2. The design method of an active suspension omnidirectional robot chassis assembly according to claim 1, characterized in that: The chassis frame design in step S1 includes the following steps: S1.

1. The triangular main frame is composed of three large-diameter thin-walled aluminum square tubes. Plates and resin light-cured printed parts are embedded inside the aluminum square. The printed parts are printed with high-precision SLA light-cured resin, which ensures accuracy and good mechanical properties. The printed parts are equipped with hexagonal holes that can be embedded with self-locking nuts to achieve one-way installation; S1.

2. After the main frame is built, the finite element stress analysis is performed on the aluminum square. According to the maximum stress of the vehicle body, the maximum stress is 1.989×10 7 N / m 2 , concentrated in the middle part.

3. The design method of an active suspension omnidirectional robot chassis assembly according to claim 1, characterized in that: The AGV wheel set design in step S2 includes the following steps: S2.

1. Design of driving wheel set: In the design, a brushless motor is selected as the driving wheel set design, and a D-hole clamping coupling is selected as the coupling; S2.

2. Heading axis system design: In the design, a brushless DC motor is selected as the driving force source of the heading part, the transmission mechanism adopts shaft transmission, and the heading axis system uses cross roller bearings.

4. A design method for an active suspension omnidirectional robot chassis assembly according to any one of claims 1 or 3, characterized in that: The outer layer material of the rubber-coated wheel in the driving wheel set is polyurethane with a hardness of 55a.

5. The design method of an active suspension omnidirectional robot chassis assembly according to claim 1, characterized in that: In the control design of the active suspension in step S3, the active suspension can adjust some parameters in real time according to the road conditions, such as the height of the chassis relative to the ground, the damping rebound rate, and the hardness of the suspension (K value). For flat roads, the active suspension system can reduce the contact area between the chassis and the road surface. When the system is powered off, it is necessary to ensure that the vehicle body has a basic supporting force so that the vehicle body chassis does not contact the ground. Therefore, the active suspension system needs to have a certain supporting force even when the power is off. There are two options for the design of the mechanism here: mechanical limit or low K value spring, and the parameters of the spring are designed as follows: According to the chassis weight of the vehicle, and then according to the gravity calculation formula G=mg (3-1) The gravity value of the vehicle body is obtained. Since the vehicle body is a three-steering wheel mechanism with three contact points with the ground, the force value of each supporting wheel group and the stroke value of the shock absorber with installed spring are obtained. Under this condition, the spring k value is designed. The k value design formula is as follows: Where: G represents the rigidity modulus corresponding to the spring material, d represents the wire diameter, D m Represents the spring outer diameter D o Subtract wire diameter d; N c Represents the effective number of coils, which is the total number of coils of the spring minus 2.

6. The design method of an active suspension omnidirectional robot chassis assembly according to claim 5, characterized in that: In the control design of the active suspension in step S3, when there is an initial amount (shock absorber) and the electric active suspension on the chassis starts to work, the additional damping and supporting force mechanism is designed, taking into account the space utilization and mechanism execution efficiency, and using a brushless motor driven gear rack to provide. In principle, the gear rack mechanism driven by the FOC motor can generate additional different torques and damping under different working modes of the driving motor and different PID values, thereby changing the height and hardness of the suspension. According to the torque transmission formula: F=M / L (3-3) In the process of converting torque into supporting force, it is divided by the force transmission distance. The smaller the distance, the greater the equivalent supporting force obtained, and the smaller the outer diameter of the gear parameter should be, the better.

7. A method for designing an active suspension omnidirectional robot chassis assembly according to any one of claims 5 or 6, characterized in that: In the control design of the active suspension in step S3, it is not appropriate to change the height simply by means of a gear rack because of the existence of the shock absorber. This is because when the chassis is lifted, if the shock absorber fixing point remains unchanged, the wheel set is lifted relative to the chassis, and the shock absorber compression is reduced, and the motor output torque is greater. When the vehicle body is lifted to the highest point, the shock absorber returns to its original length, and the RoboMaster M2006 alone cannot support the vehicle body. Therefore, the shock absorber mechanism needs to be lifted together to achieve the lifting of the entire mechanism. In order to achieve self-locking at different heights, a trapezoidal screw mechanism is selected. The lead selection is calculated based on the height that the active suspension can be raised and the peak speed of the drive motor. The screw is selected for compatibility, and a calculation and verification analysis is performed on it. The screw mechanism is verified as follows: According to the parameters of the trapezoidal screw, determine the outer diameter d, pitch p, middle diameter d2, and tooth angle α of the screw; According to the lead L value, the formula for calculating the number of lines of the screw is as follows n=L / p (3-4) Calculate the number of threads n of the screw and the helix angle β: β=arctan(L / πd2) (3-5) The β value is obtained. According to the material properties of 304 stainless steel, the allowable stress σ value and the allowable shear stress τ value of the screw are determined. According to the static load F value, the axial stress σ1 of the screw is calculated as σ1=F / π(d2-2) / 4 (3-6) The calculated σ1 value is less than the allowable stress σ. Axial stress refers to the compressive or tensile stress in the axial direction of the screw, which is used to check whether the screw is buckled or broken. According to the static load F value, the shear stress τ1 formula of the screw is calculated The τ1 value obtained is less than the allowable shear stress τ.

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