CN220996566U - Flexibly movable wheel leg type mobile unit - Google Patents

Abstract

The wheel leg type mobile unit capable of flexibly acting comprises a frame, a four-bar leg mechanism and an omnidirectional roller mechanism; the rack comprises a bottom plate and side plates fixedly connected to two sides of the bottom plate; the two groups of four-bar leg mechanisms are respectively connected to two sides of the frame; the four-bar leg mechanism comprises a motor A, an upper bar, a lower bar and a driving rod; the two groups of all-directional roller mechanisms are respectively connected to the lower ends of the lower connecting rods of the two groups of four-connecting-rod leg mechanisms. The utility model provides a mobile robot with a foot structure and a wheel structure, wherein the foot structure is a biped structure based on a four-bar mechanism, and has the advantages of simple structure, stable mechanism and simple control strategy compared with the biped structure, and the wheel structure is arranged at the lower end of the foot structure, and drives a roller to do circumferential rotation through a motor B and drives the roller to do horizontal rotation through a motor C, so that the movement flexibility of a mobile unit is greatly expanded.

Description

Flexibly movable wheel leg type mobile unit

Technical Field

The utility model relates to the technical field of robot moving/advancing structures, in particular to a wheel leg type moving unit capable of flexibly acting.

Background

With the rapid development of the robot industry, various robots are continuously emerging, wherein the mobile robots are the most widely applied type, and can see the images and the shadows in the fields of logistics storage, military exploration, rescue and relief work, outdoor transportation, home service and the like.

The movable robot can be divided into foot type, wheel type and crawler type according to the driving mode, and the three types have advantages and disadvantages and application scenes. The foot robot has the characteristics of good terrain adaptability and flexible action (complex action gesture can be realized), but has higher control difficulty, and is suitable for rugged road surfaces or road surfaces with more obstacles. The wheeled robot has the characteristics of high land leveling speed and easiness in control, has certain requirements on road conditions, and is suitable for a road surface without or with few obstacles and relatively flat.

Along with the continuous expansion of the application field of the mobile robot, the requirements of people on the motion performance of the mobile robot are also higher and higher, and a pure wheel type or foot type or crawler type robot cannot well play a role in certain specific fields. Therefore, in order to widen the application scene and the working field of the mobile robot, the mobile robot with the combination of two driving modes is developed (for example, the invention patent with the publication number of CN112078678A, namely a deformable composite chassis of a nuclear emergency robot and an application method thereof, discloses a crawler-type and wheel-type combined mobile robot), so that the advantages of different driving modes are combined, and the method becomes an important research direction of robot researchers at home and abroad.

Disclosure of Invention

The utility model aims to overcome the defects of the prior art and provide the wheel leg type mobile unit capable of flexibly acting, which is applied to a mobile robot, combines the advantages of a wheel type structure and a foot type structure, and provides a prerequisite foundation for widening the application scene and the working field of the mobile robot.

The technical scheme of the utility model is as follows: the wheel leg type mobile unit capable of flexibly acting comprises a frame, a four-bar leg mechanism and an omnidirectional roller mechanism;

the rack comprises a bottom plate and side plates fixedly connected to two sides of the bottom plate;

The two groups of four-bar leg mechanisms are respectively connected to two sides of the frame; the four-bar leg mechanism comprises a motor A, an upper bar, a lower bar and a driving rod; the motor A is arranged on one side of the bottom plate and is adjacently arranged with one of the two side plates, and the shaft of the motor A is parallel to the bottom plate and extends out of the bottom plate; the upper end of the upper connecting rod is hinged to a side plate adjacent to the motor A, and the lower end of the upper connecting rod is hinged to the upper end of the lower connecting rod; one end of the driving rod is fixedly arranged on the shaft of the motor A, the other end of the driving rod is hinged on the lower connecting rod, and the driving rod is driven by the motor A to rotate so as to drive the upper connecting rod to be linked with the lower connecting rod, so that the included angle between the upper connecting rod and the lower connecting rod is changed;

the two groups of all-directional roller mechanisms are respectively connected to the lower ends of the lower connecting rods of the two groups of four-connecting-rod leg mechanisms.

The utility model further adopts the technical scheme that: the omnidirectional roller mechanism comprises a base plate, a hinge shaft, a rotating shaft, a roller seat, rollers, a roller shaft, a motor B, a motor C and a gear pair; ear parts for installing the hinge shaft are fixedly arranged on two sides of the upper end of the base plate, and shaft holes for the hinge shaft to pass through are formed in the ear parts; the hinge shaft is rotatably arranged in the shaft holes of the two lugs and is axially limited, and one end of the hinge shaft is connected with the lower end of the lower connecting rod; the rotating shaft is perpendicular to the base plate, is rotatably arranged on the base plate and is axially positioned, and two ends of the rotating shaft are respectively positioned at the upper end and the lower end of the base plate; the roller seat is fixedly connected to the lower end of the rotating shaft; the idler wheel is rotatably arranged on the idler wheel seat through an idler wheel shaft; the motor B is fixedly arranged on the roller seat, and the shaft of the motor B is connected with the roller shaft through a coupler; the motor C is fixedly arranged at the upper end of the base plate, and the shaft of the motor C extends out perpendicular to the base plate; the gear pair comprises a driving gear and a driven gear, the driving gear is fixedly arranged on the shaft of the motor C, and the driven gear is fixedly arranged at the upper end of the rotating shaft and meshed with the driving gear.

The utility model further adopts the technical scheme that: the upper end of the bottom plate is fixedly connected with an accessory mounting rack; the upper end of the accessory mounting rack is provided with a positioning hole A and a positioning hole B, and a bottom plate is respectively provided with a bayonet A and a bayonet B under the positioning hole A and the positioning hole B;

The system also comprises a battery module, a vision module, an attitude sensor, an encoder and a singlechip; the battery module is inserted into the bayonet A of the bottom plate through a positioning hole A on the accessory mounting rack and is electrically connected with each electric component; the vision module comprises a camera and an image processing chip, wherein the camera is inserted into a bayonet B of the bottom plate through a positioning hole B on the accessory mounting frame and is used for acquiring surrounding environment information, and the image processing chip is electrically connected with the camera and is used for providing image processing operation related to a robot vision algorithm; the attitude sensor is fixedly arranged on the bottom plate and is used for acquiring attitude information data of the frame; the encoders are respectively and electrically connected with the motor A, the motor B and the motor C in a one-to-one correspondence manner, and each encoder controls the operation of one motor; the singlechip is fixedly arranged on the bottom plate, the signal input port of the singlechip is respectively and electrically connected with the image processing chip and the attitude sensor, and the signal output port of the singlechip is electrically connected with the encoder.

The utility model further adopts the technical scheme that: the four-bar linkage leg mechanism also includes a shock absorbing assembly. The damping component comprises a sleeve, an end cover, a connecting rod and a spring; the inside of the sleeve is provided with an inner hole with one end being closed and the other end being open, the two sleeves are respectively hinged on the upper connecting rod and the driving rod at the closed ends, and the openings of the two sleeves are oppositely arranged; the two end covers are respectively and fixedly arranged at the openings of the two sleeves, and a rod penetrating hole is formed in the center of each end cover; the connecting rod comprises a small-diameter section and large-diameter sections fixedly connected to two ends of the small-diameter section, the large-diameter sections at two ends of the connecting rod are respectively in sliding fit with inner holes of the two sleeves, and two ends of the small-diameter section of the connecting rod respectively penetrate through rod penetrating holes in the two end covers; when the large-diameter section of the connecting rod moves to abut against the end face of the end cover or the closed end of the inner hole of the sleeve, the connecting rod reaches the limit position; the spring is sleeved on the small-diameter section of the connecting rod, and two ends of the spring respectively prop against the end faces of the two end covers.

The utility model further adopts the technical scheme that: the battery module selects a model airplane battery, the camera selects a binocular camera, the image processing chip selects Jetson Nano edge computing development boards, the attitude sensor selects an MPU-6050 gyroscope, the encoder selects an AS5147P magnetic rotating position sensor, and the singlechip selects an ESP32 microcontroller.

The utility model further adopts the technical scheme that: the wireless remote controller also comprises a wireless transmission module and a wireless remote controller; the wireless transmission module is electrically connected with the singlechip and is connected with the wireless remote controller in a wireless communication mode.

The utility model further adopts the technical scheme that: the wireless transmission module is a wireless serial port module, and the wireless remote controller is a Xinjiang wireless remote controller.

Compared with the prior art, the utility model has the following advantages:

1. The utility model provides a portable robot that foot formula structure and wheeled structure combined together, wherein, foot formula structure is based on four-bar linkage's biped structure, compares many foot structures (four feet, six feet, eight feet) and has simple structure, mechanism stability and control strategy are simple advantage, and wherein, wheeled structure establishes at foot formula structure's lower extreme, and it is through motor B driving roller circular rotation, is through motor C driving roller horizontal rotation to greatly extended the removal flexibility of mobile unit.

2. The combination of the foot-type structure and the wheel-type structure has the following advantages:

The four-bar leg mechanism can perform active vibration isolation, namely, the motion track of the trunk (rack) is decoupled from the track of the foot end (roller), so that the trunk of the mobile unit can be kept stable on a fluctuant road surface; when encountering ground obstacles, the four-bar leg mechanisms at one side or two sides of the frame can be adaptively deformed, so that the frame is kept stable and horizontal, and the adaptability to rugged road surfaces is improved;

II, the double-wheel moving mode can realize zero-radius turning, so that the overall movement flexibility of the mobile unit is improved; the wheel type structure can realize low-power-consumption rapid movement on flat ground and can adapt to rugged topography with smaller degree.

The utility model is further described below with reference to the drawings and examples.

Drawings

FIG. 1 is a schematic view of the structure of the present utility model at a first viewing angle;

FIG. 2 is a schematic view of the structure of the present utility model at a second view angle;

fig. 3 is a view of the present utility model in a state where the one-sided roller passes over an obstacle (view angle 1);

fig. 4 is a view of the present utility model when the one-sided roller passes over an obstacle (view 2);

FIG. 5 is a schematic illustration of the assembly relationship of the shock absorbing assembly in a four-bar leg mechanism;

FIG. 6 is a schematic diagram of the assembly relationship of the parts in the omni-directional roller mechanism;

FIG. 7 is a schematic diagram showing the electrical connection relationship between the electrical components according to the present utility model.

Legend description: a bottom plate 11; bayonet A111; bayonet B112; a side plate 12; an accessory mounting bracket 13; a positioning hole a131; positioning holes B132; a motor a21; an upper link 22; a lower link 23; a drive lever 24; a sleeve 25; end cap 26; a connecting rod 27; a spring 28; a substrate 31; an ear 311; a hinge shaft 32; a rotation shaft 33; a roller seat 34; a roller 35; a roller shaft 36; a motor B37; a motor C38; a drive gear 391; a driven gear 392; a battery module 4; a camera 51; an image processing chip 52; a posture sensor 6; an encoder 7; a singlechip 8; a wireless transmission module 91; a wireless remote control 92.

Detailed Description

Example 1:

As shown in fig. 1-7, the flexibly moveable wheel-leg type mobile unit comprises a frame, a four-bar leg mechanism and an omnidirectional roller mechanism.

The frame comprises a bottom plate 11 and side plates 12 fixedly connected to two sides of the bottom plate 11.

The two groups of four-bar leg mechanisms are respectively connected to two sides of the frame. The four-bar leg mechanism includes a motor a21, an upper link 22, a lower link 23, and a drive lever 24. The motor a21 is mounted on one side of the bottom plate 11 and is disposed adjacent to one of the two side plates 12 with its axis parallel to the bottom plate 11 and protruding outward of the bottom plate 11. The upper end of the upper link 22 is hinged to one of the side plates 12 adjacent to the motor a21, and the lower end of the upper link 22 is hinged to the upper end of the lower link 23. One end of the driving rod 24 is fixedly arranged on the shaft of the motor A21, the other end of the driving rod 24 is hinged on the lower connecting rod 23, and the driving rod 24 rotates under the driving of the motor A21 so as to drive the upper connecting rod 22 and the lower connecting rod 23 to link, so that the included angle between the upper connecting rod 22 and the lower connecting rod 23 is changed.

The two groups of all-directional roller mechanisms are respectively connected with the lower ends of the lower connecting rods 23 of the two groups of four-connecting-rod leg mechanisms. The omnidirectional roller mechanism comprises a base plate 31, a hinge shaft 32, a rotating shaft 33, a roller seat 34, a roller 35, a roller shaft 36, a motor B37, a motor C38 and a gear pair. Ear portions 311 for installing the hinge shaft 32 are fixedly arranged on two sides of the upper end of the base plate 31, and shaft holes for the hinge shaft to pass through are formed in the ear portions 311. The hinge shaft 32 is rotatably installed in shaft holes of the two ears 311 and is axially limited, and one end of the hinge shaft 32 is connected to the lower end of the lower link 23. The rotation shaft 33 is disposed perpendicularly to the base plate 31 and rotatably mounted on the base plate 31 and axially positioned with both ends thereof being located at the upper end of the base plate 31 and the lower end of the base plate 31, respectively. The roller seat 34 is fixedly connected to the lower end of the rotating shaft 33. The roller 35 is rotatably mounted on the roller mount 34 by a roller shaft 36. The motor B37 is fixedly mounted on the roller mount 34, and its shaft is connected to the roller shaft 36 through a coupling. The motor C38 is fixedly mounted on the upper end of the base plate 31 with its spindle extending perpendicularly to the base plate 31. The gear pair includes a driving gear 391 and a driven gear 392, the driving gear 391 is fixedly installed on the shaft of the motor C38, and the driven gear 392 is fixedly installed on the upper end of the rotation shaft 33 and is engaged with the driving gear 391.

Preferably, the upper end of the base plate 11 is fixedly connected with an accessory mounting bracket 13. The upper end of the accessory mounting rack 13 is provided with a positioning hole A131 and a positioning hole B132, and the bottom plate 11 is respectively provided with a bayonet A111 and a bayonet B112 under the positioning hole A131 and the positioning hole B132.

Preferably, the four-bar linkage leg mechanism further comprises a shock absorbing assembly. The shock absorbing assembly comprises a sleeve 25, an end cap 26, a connecting rod 27 and a spring 28; an inner hole with one end closed and the other end open is arranged in the sleeve 25, the two sleeves 25 are respectively hinged on the upper connecting rod 22 and the driving rod 24 at the closed ends, and the openings of the two sleeves 25 are oppositely arranged; the two end covers 26 are respectively and fixedly arranged at the openings of the two sleeves, and a rod penetrating hole is formed in the center of each end cover 26; the connecting rod 27 comprises a small-diameter section 271 and large-diameter sections 272 fixedly connected to two ends of the small-diameter section, the large-diameter sections 272 at two ends of the connecting rod 27 are respectively in sliding fit with inner holes of the two sleeves 25, and two ends of the small-diameter section 271 of the connecting rod 27 respectively penetrate through rod penetrating holes of the two end covers 26; when the large diameter section 272 of the connecting rod 27 moves to abut against the end face of the end cover 26 or the closed end of the inner hole of the sleeve 25, the connecting rod 27 reaches the limit position; the spring 28 is sleeved on the small-diameter section 271 of the connecting rod 27, and two ends of the spring 28 respectively prop against the end faces of the two end covers 26. Based on the setting of damper, be used for the shock attenuation on the one hand, the buffering is favorable to maintaining the frame steady because of the vibrations that the road surface unevenness arouses, protects components and parts in the frame, on the other hand has restricted the rotation angle of upper connecting rod and lower connecting rod to a certain extent, avoids too big or undersize rotation angle to lead to four connecting rod shank mechanism card to die.

Preferably, the flexibly movable wheel leg type mobile unit further comprises a battery module 4, a vision module, an attitude sensor 6, an encoder 7 and a singlechip 8. The battery module 4 is inserted into the bayonet a111 of the base plate 11 through the positioning hole a131 on the accessory mounting bracket 13, and is electrically connected with each electric component. The vision module comprises a camera 51 and an image processing chip 52, wherein the camera 51 is inserted into a bayonet B112 of the base plate 11 through a positioning hole B132 on the accessory mounting frame 13 and is used for acquiring surrounding environment information, and the image processing chip 52 is electrically connected with the camera and is used for providing image processing operation related to a robot vision algorithm. The attitude sensor 6 is fixedly mounted on the base plate 11, and is used for acquiring attitude information data of the frame. A plurality of encoders 7 are electrically connected to the motor a21, the motor B37, and the motor C38 in a one-to-one correspondence, respectively, and each encoder 7 controls the operation of one motor (the motors are collectively referred to as the motor a21, the motor B37, and the motor C38). The singlechip 8 is fixedly arranged on the bottom plate 11, the signal input port of the singlechip is respectively and electrically connected with the image processing chip 52 and the attitude sensor 6, and the signal output port of the singlechip is electrically connected with the encoder 7.

Preferably, the battery module 4 selects a model airplane battery, the camera 51 selects a binocular camera, the image processing chip 52 selects Jetson Nano edge calculation development boards, the attitude sensor 6 selects an MPU-6050 gyroscope, the encoder 7 selects an AS5147P magnetic rotation position sensor, and the singlechip 8 selects an ESP32 microcontroller.

Preferably, the flexibly movable wheel-leg type mobile unit further includes a wireless transmission module 91 and a wireless remote control 92. The wireless transmission module 91 is electrically connected with the singlechip 8, the wireless transmission module 91 is connected with the wireless remote controller 92 in a wireless communication mode, the wireless transmission module 91 is a wireless serial port module, and the wireless remote controller 92 is a Xinjiang wireless remote controller.

Brief description of the utility model uses:

the wheel leg type mobile unit capable of flexibly acting is applied to the mobile robot, and combines the advantages of the foot type structure and the wheel type structure.

Referring to fig. 1-2, in the omnidirectional roller mechanism (foot-type structure), a motor B37 is used for driving the roller 35 to rotate, providing power for running of the wheel leg type moving unit, the number of the motors B37 is two, one motor B37 is used for controlling rotation of one roller 35, differential steering can be achieved through different rotation speeds of the two rollers 35, and a motor C38 drives the roller seat 34 and the roller 35 to horizontally rotate through power transmission of a gear pair, so that in-situ zero-radius steering or turning can be achieved.

Referring to fig. 3 to 4, in the four-bar leg mechanism, the two groups of four-bar leg mechanisms are controlled to be elastically deformed by motors a21 respectively included in the four-bar leg mechanisms, when the included angle between the upper bar 22 and the lower bar 23 is increased, the four-bar leg mechanism is elongated in the vertical direction, when the included angle between the upper bar 22 and the lower bar 23 is decreased, the four-bar leg mechanism is shortened in the vertical direction, and when encountering a ground obstacle, the four-bar leg mechanism on one side or both sides of the frame is adaptively deformed, so that the frame is kept stable and horizontal.

Regarding the selection and demonstration of the singlechip:

if the wheel leg type mobile unit is required to complete a series of functions and tasks, the choice of the brain is determined first, so that the selection of the singlechip is put into the first place, and the following are some MCUs which are currently mainstream, and the following are selected according to design requirements and cost performance.

Scheme one: raspberry pie was used as the controller. The raspberry pie has the advantages of small and exquisite appearance, powerful internal functions, good CPU performance, high speed, high resolution, fast data transmission and more memory choices, can realize more complex task management, can provide IO pins, and directly controls other bottommost hardware. However, raspberry pie is relatively expensive and this solution is abandoned for economic reasons.

Scheme II: the STC12C5A60S2 singlechip of STC company is adopted as a controller, the STC12C5A60S2 singlechip has low power consumption, high running speed and strong capability of resisting external interference, the instruction of the STC12C5A60S2 singlechip can be completely fused with the ancient 8051, the speed is increased by 8-12 times (compared with the 8051), and the design requirement can be met. However, the development ecology is not perfect compared with other chips in consideration of the fact that the chip has less data, so that the scheme is abandoned.

Scheme III: the STC89C52 microprocessor of STC company is used as a controller, the STC89C52 microprocessor is provided with 8K programmable Flash memory, and flexible 8-bit CPU and programmable Flash are reserved, so that various embedded applications with high flexibility and high efficiency can be provided. However, considering that the motion and posture control of the wheel leg type mobile unit is slightly complicated, there is a fear that the performance of the STC89C52 microprocessor is very likely to be unable to perfectly perform various functions, so this scheme is abandoned.

Scheme IV: based on STM32 of ST company, STM32 is a 32-bit microprocessor taking ARM7 as a core, and simulation and tracking at any time are supported. The ARM core architecture is adopted, the real-time performance of the ARM core architecture is excellent, the power consumption control part is quite outstanding, the types of matched external equipment are more, the ARM core architecture is convenient to develop, and the ARM core architecture can be rapidly put into the market.

Scheme five: based on ESP32 of national music Xin technology company, ESP32 is a low-cost, low-power-consumption and high-performance microcontroller, which is an upgrade version of ESP8266, and has more GPIO pins, higher processing speed, better Wi-Fi and Bluetooth connection capability and more memory. ESP32 has two processor cores, a main core and an auxiliary core, which may make the system more efficient in multitasking. ESP32 has excellent power saving characteristics and can enter a deep sleep state when high performance is not required to reduce power consumption.

In summary, the MCU selects the STM32 and the ESP32, and the two chips have advantages and disadvantages, and the usage scenario is different, but the usage scenario cannot be selected at any time, but because the need to drive the brushless motor is considered, the ESP32 is found to have a good development environment and perfect SimpleFOC library files, and the driving of the brushless motor can be conveniently made, so that the ESP32 is finally selected as the main control chip of the wheel-leg mobile unit (i.e. the above-mentioned singlechip 8), and the STM32 is only used as the main control chip of the wireless remote controller 92.

Selection and demonstration of the motor:

Since the basic functions of the wheel-leg type mobile unit are all built on the standard of vertical balance, the second part is to determine the type of motor, and the following are some motors which are mainstream in the market, and the following are selected according to design requirements and cost performance.

Scheme one: miniature DC motors are often the first choice for miniature applications such as robots and toy vehicles because of their small size, light weight, moderate power and relatively low cost. The miniature direct current motor has the advantages of high response speed, high rotating speed, easiness in control and the like. However, the miniature direct current motor has large rotation speed fluctuation and is easy to stall, so that the miniature direct current motor is abandoned in the design.

Scheme II: the stepping motor has the advantages of high control precision, low rotating speed, stable operation and the like, and is generally used for applications requiring accurate positioning and angle control. Compared with a miniature direct current motor, the stepping motor has stable rotating speed, but smaller power, larger volume and weight and higher cost. The use of stepper motors is therefore abandoned in the present design.

Scheme III: brushless direct current motors, which employ brushless motors, have the advantages of high efficiency, low noise, long life, etc., and are generally used in applications requiring high speed and high power. Brushless dc motors have higher rotational speeds but also higher costs than miniature dc motors and stepper motors.

In summary, the use of brushless motor driven leg motor units has significant advantages, such as relatively high rotational speeds and power, and higher speeds and accelerations, which allow for more flexible robot motion control. Meanwhile, the brushless motor has a simple structure, is not easy to damage and has a longer service life. Therefore, a brushless direct current motor (the motor A, the motor B and the motor C are all brushless direct current motors) is finally adopted to power the wheel leg type mobile unit.

Selection and demonstration of magnetic encoder chips:

After determining the drive motor, it is necessary to consider how precisely the motor is controlled, and if it is desired to precisely control the motor, the encoder chips, which are the ones that are currently on the market, are selected according to design requirements and cost performance.

Scheme one: AS5600: the 12-bit magnetic rotary position sensor with high resolution and low power consumption can realize 360-degree angle measurement without dead angles. The chip has the advantages of low cost, low power consumption and high resolution, and is suitable for small-sized low-power consumption applications. This solution is abandoned because the accuracy of the position of the motor is high in the upright control of the wheel-leg mobile unit, compared to the accuracy of the magnetic encoder chip of the other type.

Scheme II: AS5048A: a magnetic rotary position sensor with 14 bit resolution supports a variety of interfaces such as PWM, SSI, and BiSS-C. The chip has the advantages of high resolution, high precision and high reliability, and is suitable for applications requiring high precision and high stability. The chip has higher precision, high price and low cost performance, so the scheme is abandoned.

Scheme III: m72472: a three-axis magnetic sensor that can provide measurements at 12-bit resolution. The chip has the advantages of high resolution, strong anti-interference performance and high reliability, and is suitable for applications requiring high precision and high reliability. This solution is abandoned because the accuracy of the position of the motor is high in the upright control of the wheel-leg mobile unit, compared to the accuracy of the magnetic encoder chip of the other type.

Scheme IV: AS5147P: a14-bit magnetic rotary position sensor with high resolution and low power consumption supports an SPI interface. The chip has the advantages of high resolution, low power consumption and high response speed, and is suitable for applications requiring high resolution and high response speed.

In summary, AS5147P is most suitable for the design of a wheel-leg mobile unit, on one hand, supports SPI communication, and can be well combined with an MCU to obtain position information of a motor, and on the other hand, has higher accuracy and faster response. AS5147P is thus ultimately employed AS a magnetic encoder chip (i.e. encoder 7 described above).

Selection and demonstration of attitude sensor:

The wheel leg type mobile unit is required to keep balance, firstly, the self gesture is determined, and according to the gesture information, how to adjust is calculated, so that a proper gesture sensor is particularly important, the following are main gesture sensors on the market, and the following are selected according to design requirements and cost performance.

Scheme one: MPU-6050: the IMU is a classical 6-degree-of-freedom IMU, consists of a three-axis gyroscope and a three-axis accelerometer, and can be communicated with a microcontroller through an I2C interface. The advantages are low cost, stable performance, and wide application in DIY robots and embedded systems. The disadvantage is the relatively low accuracy and is not suitable for high accuracy applications.

Scheme II: MPU-9250: the IMU integrated with the 9-degree-of-freedom (9-doF) sensor comprises a three-axis gyroscope, a three-axis accelerometer and a three-axis magnetometer, and can communicate with a microcontroller through an SPI or I2C interface. The device has the advantages of comprehensive functions and higher precision, and is suitable for some applications with higher requirements on the precision of gesture measurement. The disadvantage is the relatively high price.

Scheme III: BNO055: the IMU integrated with the 9-degree-of-freedom (9-doF) sensor and the sensor fusion algorithm comprises a three-axis gyroscope, a three-axis accelerometer, a three-axis magnetometer and a temperature sensor, and can be communicated with a microcontroller through an I2C or SPI interface. The method has the advantages of high integration level, high gesture resolving precision and suitability for some applications with high requirements on gesture precision. The disadvantage is the relatively high price.

Scheme IV: LSM9DS1: the IMU integrated with the 9-degree-of-freedom sensor comprises a three-axis gyroscope, a three-axis accelerometer and a three-axis magnetometer, and can be communicated with a microcontroller through an SPI or I2C interface. The method has the advantages of moderate price and higher precision, and is suitable for some applications with higher requirements on the precision of gesture measurement. The disadvantage is the relatively low integration level, which requires the processing of a sensor fusion algorithm.

In summary, in the design of the wheel-leg type mobile unit, there is no very high requirement on the posture of the posture sensor, and both the MPU-6050 and the LSM9DS1 are good choices in consideration of cost performance, and the MPU6050 is finally selected as the posture sensor 6 in consideration of convenience of use.

Selection and demonstration of wireless transmission modules:

In the design of the wheel-leg mobile unit, the wireless remote controller is required to control each function, so that a proper wireless communication scheme is necessary to be selected, and the following wireless transmission modules are mainstream in the market, and the following wireless transmission modules are selected according to the requirement and cost performance.

Scheme one: bluetooth is a widely applied wireless communication technology and is suitable for the fields of mobile equipment, consumer electronics, medical equipment and the like. The Bluetooth communication distance is far, communication can be realized within the range of 10-100 meters, and multi-device connection is supported. Bluetooth communication rates are slow, typically below 1Mbps, and are not suitable for high-speed data transmission.

Scheme II: wi-Fi is a high-speed and large-bandwidth wireless communication technology, and is suitable for the fields of families, enterprises, public places and the like. Wi-Fi communication speed is fast, can reach tens Mbps or hundreds Mbps, supports many equipment connection. However, wi-Fi has high power consumption, requires high hardware cost and complexity, and is not suitable for low-cost applications.

Scheme III: radio frequency is a wireless technology suitable for long-distance communication, and is mainly used in the fields of telecommunication, radio, remote control and the like. The radio frequency communication distance is far, and communication can be realized in the range of tens of kilometers to hundreds of kilometers, so that large data transmission is supported. But is greatly affected by interference, unstable in communication and easy to eavesdrop and interfere.

Scheme IV: the wireless serial port is a wireless technology suitable for short-distance communication and is mainly used for wireless communication of embedded equipment such as a singlechip, a sensor and the like. The communication distance of the wireless serial port is generally within tens of meters, the communication speed is high, the range from hundreds of Kbps to several Mbps can be reached, and the connection of multiple devices is supported. But the wireless serial communication has poor safety and is easy to be intercepted and interfered. Its advantages are moderate communication distance, high communication speed and supporting multiple devices.

In summary, in the design of the wheel-leg mobile unit, the wireless serial port module is selected as the wireless transmission module 91 in consideration of simplicity and stability of operation and design.

Selection and demonstration of power supply scheme:

The determination of the power supply mode has a relatively large influence on the performance of the wheel-leg mobile unit, and the following are several common power supply schemes, which are selected according to design requirements.

Scheme one: battery powered, which is the simplest power scheme, connects the battery directly to the power input of the robot, for example through a plug such as JST or XT 30. Different types, capacities and voltages of batteries may be selected, such as lithium batteries, nickel hydrogen batteries, lead acid batteries, and the like. The method has the advantages of simple scheme, easy operation and suitability for small robots. The disadvantage is that the battery capacity is limited and requires frequent replacement or recharging.

Scheme II: the model airplane battery is powered by a lithium battery technology, and has the characteristics of high capacity, high discharge rate, portability and the like. They can be directly connected to the power input of the robot, typically using a standard XT-60 plug connector. The advantages are that: the high-capacity high-discharge-rate light-weight high-voltage power supply has the advantages of high capacity, high discharge rate, portability and the like, can provide a stable power supply, and is suitable for application scenes requiring longer working time.

In summary, considering that the driving current required by the peripheral equipment of the wheel-leg type mobile unit is large, a power supply scheme with high discharging capacity is required to be selected, and finally, a model airplane battery is selected to be used for power supply.

Analysis and selection of cameras:

Compared with a monocular vision camera, the binocular vision camera has better depth of field sense and three-dimensional measurement capability, and can provide more accurate depth information, so that the implementation of an obstacle avoidance algorithm is relatively easier, the multi-view image information of the binocular vision camera is also beneficial to improving the recognition rate of objects, and the efficiency of real-time return and real-time processing of images can be improved. The binocular camera REALSENSE D435i available under Jetson Nano platform was used in the selection of a particular camera.

Analysis and selection of image processing chips:

The Jetson Nano edge computing development board is provided with a four-core ARM 'Cortex-A57' CPU and 128 NVIDIA 'Maxwell' GPU cores, has strong computing capacity, can rapidly process image data, and accelerates the operation of a robot vision algorithm. Hardware and software of the Jetson Nano edge computing development board support a plurality of AI algorithms and frameworks, such as TensorRT, caffe, pyTorch, openCV, and the like, so that a developer can conveniently perform visual and voice tasks such as object identification, target tracking, automatic obstacle avoidance and the like.

The Jetson Nano edge computing development board has the size of only 69.6mm multiplied by 45mm, is very small and portable, is suitable for embedded and robot application, can be connected with various peripherals such as cameras, buzzers, sensors and the like, provides various interfaces such as USB3.0 and HDMI, ethernet, and is very convenient for a developer to debug and deploy. The power consumption of the Jetson Nano-watt edge computing development board is only 5 watts, and the method is very suitable for a low-power consumption embedded system and a robot application scene needing long-time work. Therefore, jetson Nano edge computing development boards were selected as the image processing chips 52.

The utility model relates to the selection of a software scheme, which comprises the following steps:

1. Singlechip data processing scheme

For the posture information data read from the posture sensor 6 (MPU 6050) by the single chip microcomputer 8 (ESP 32), a filtering process is generally required to remove noise and instability to improve the stability and accuracy of the control system. The common gesture filtering algorithm comprises Kalman filtering, complementary filtering, moving average filtering and the like, and the data of the MPU6050 are processed by the Kalman filtering after comparison, and the Kalman filtering has the advantage that signals containing noise and uncertainty can be effectively filtered and estimated.

2. Frame balance maintaining scheme

The control algorithm for the bipedal robot to maintain equilibrium upright typically uses a PID control algorithm. The PID controller calculates the control amount based on the deviation (i.e., the difference between the desired output and the actual output), the integral, and the derivative. With the balance standing, the desired output is zero, the deviation is the difference between the current attitude angle and the target attitude angle. The controller controls the gesture of the robot by adjusting the rotating speed of the motor so as to achieve the purpose of balancing and standing.

However, the single loop PID control can achieve basic upright control for the balance control of the bipedal robot, but there may be some problems in practical application, for example, the moving speed of the robot may not be 0. This is because the single loop PID control can only control the response speed and stability of the system by adjusting the PID parameters of the controller, but cannot solve the problems of nonlinearity, time variation, coupling, etc. existing in the system.

Thus, a cascade PID is chosen, which is a control structure of a PID controller, consisting of 24 two or more PID controllers, the output of one of which is connected to the input of the other. In the control of a bipedal robot, tandem PID can be used to better control the attitude and speed of the vehicle body. Specifically, the cascade PIDs may be divided into an outer loop PID and an inner loop PID. The outer loop PID generally controls the attitude of the system, such as the tilt angle of a bipedal robot. The inner loop PID generally controls the speed of the system, such as the rotational speed of a bipedal robot. The value output by the outer loop PID controller is used as an input to the inner loop PID controller, and the output value of the inner loop PID controller is used to control the actual system operation. The structure has the advantages that the outer ring PID controller can better control the gesture of the system, so that the input of the inner ring PID controller is more stable, and the performance of the whole system is improved. In the control of the double-wheel-foot robot, the cascade PID can enable the system to be more stable and control the inclination angle and speed of the vehicle body more accurately, so that a better balanced and vertical effect is achieved.

3. The brushless direct current motor control scheme comprises the following steps:

the Vector Control (Vector Control) of ESP32 (the above-selected SCM 8 model) + SimpleFOC is a motor Control algorithm, also called magnetic field directional Control (Field Oriented Control, FOC), which can Control the magnetic field direction and magnitude of the brushless motor, thereby realizing accurate Control of the motor.

The vector control algorithm can convert the rotation of the rotor of the three-phase brushless motor into the directional control of the magnetic field on the two-phase stator, so that the high-efficiency and accurate motor rotation speed and torque control can be realized. Such algorithms require measuring the position and speed information of the motor, typically by means of encoders, hall sensors or Back EMF (Back EMF) or the like. Vector control algorithms may be used with a variety of hardware platforms, including Arduino, ESP32, STM32, etc., and provide a simple and easy to use API interface and example program. The user may implement different control schemes for the motor, such as speed control, position control, etc., by modifying the profile. Meanwhile, simpleFOC also provides functions of various filtering algorithms, PID controllers and the like, so that a user can conveniently perform further optimization and control.

Therefore, the brushless direct current motor vector control of the wheel leg type mobile unit is realized by using the single chip microcomputer 8 (ESP 32) and SimpleFOC, and the wheel leg type mobile unit can be realized by only selecting proper hardware and motor and simultaneously learning and debugging the API interface and the configuration file of SimpleFOC.

4. Visual recognition scheme

YOLO is a real-time target detection algorithm, and can detect objects in an input image within tens of milliseconds, so that the method is suitable for scenes such as real-time return, object identification and automatic obstacle avoidance. The YOLO algorithm has high detection accuracy, can simultaneously identify and position a plurality of objects, and can detect even very small objects. In practical application, the detection rate of the object by using YOLO is lower than the detection rate of the object by using YOLO. Compared with other deep learning algorithms, the training speed of the YOLO algorithm is high, a large amount of object data can be trained rapidly, the accuracy and generalization capability of the algorithm are improved, the model is relatively small, the parameter quantity is small, and the method has the advantage of low resource occupation in embedded equipment. Accordingly, the YOLO algorithm is selected as the visual recognition scheme.

Claims (7)

1. Flexibly movable wheel leg type mobile unit, characterized by: comprises a frame, a four-bar leg mechanism and an omnidirectional roller mechanism;

the rack comprises a bottom plate and side plates fixedly connected to two sides of the bottom plate;

The two groups of four-bar leg mechanisms are respectively connected to two sides of the frame; the four-bar leg mechanism comprises a motor A, an upper bar, a lower bar and a driving rod; the motor A is arranged on one side of the bottom plate and is adjacently arranged with one of the two side plates, and the shaft of the motor A is parallel to the bottom plate and extends out of the bottom plate; the upper end of the upper connecting rod is hinged to a side plate adjacent to the motor A, and the lower end of the upper connecting rod is hinged to the upper end of the lower connecting rod; one end of the driving rod is fixedly arranged on the shaft of the motor A, the other end of the driving rod is hinged on the lower connecting rod, and the driving rod is driven by the motor A to rotate so as to drive the upper connecting rod to be linked with the lower connecting rod, so that the included angle between the upper connecting rod and the lower connecting rod is changed;

the two groups of all-directional roller mechanisms are respectively connected to the lower ends of the lower connecting rods of the two groups of four-connecting-rod leg mechanisms.

2. The flexible wheeled leg mobile unit of claim 1 wherein: the omnidirectional roller mechanism comprises a base plate, a hinge shaft, a rotating shaft, a roller seat, rollers, a roller shaft, a motor B, a motor C and a gear pair; ear parts for installing the hinge shaft are fixedly arranged on two sides of the upper end of the base plate, and shaft holes for the hinge shaft to pass through are formed in the ear parts; the hinge shaft is rotatably arranged in the shaft holes of the two lugs and is axially limited, and one end of the hinge shaft is connected with the lower end of the lower connecting rod; the rotating shaft is perpendicular to the base plate, is rotatably arranged on the base plate and is axially positioned, and two ends of the rotating shaft are respectively positioned at the upper end and the lower end of the base plate; the roller seat is fixedly connected to the lower end of the rotating shaft; the idler wheel is rotatably arranged on the idler wheel seat through an idler wheel shaft; the motor B is fixedly arranged on the roller seat, and the shaft of the motor B is connected with the roller shaft through a coupler; the motor C is fixedly arranged at the upper end of the base plate, and the shaft of the motor C extends out perpendicular to the base plate; the gear pair comprises a driving gear and a driven gear, the driving gear is fixedly arranged on the shaft of the motor C, and the driven gear is fixedly arranged at the upper end of the rotating shaft and meshed with the driving gear.

3. A flexible wheeled leg mobile unit as claimed in claim 2, wherein: the upper end of the bottom plate is fixedly connected with an accessory mounting rack; the upper end of the accessory mounting rack is provided with a positioning hole A and a positioning hole B, and a bottom plate is respectively provided with a bayonet A and a bayonet B under the positioning hole A and the positioning hole B;

The system also comprises a battery module, a vision module, an attitude sensor, an encoder and a singlechip; the battery module is inserted into the bayonet A of the bottom plate through a positioning hole A on the accessory mounting rack and is electrically connected with each electric component; the vision module comprises a camera and an image processing chip, wherein the camera is inserted into a bayonet B of the bottom plate through a positioning hole B on the accessory mounting frame and is used for acquiring surrounding environment information, and the image processing chip is electrically connected with the camera and is used for providing image processing operation related to a robot vision algorithm; the attitude sensor is fixedly arranged on the bottom plate and is used for acquiring attitude information data of the frame; the encoders are respectively and electrically connected with the motor A, the motor B and the motor C in a one-to-one correspondence manner, and each encoder controls the operation of one motor; the singlechip is fixedly arranged on the bottom plate, the signal input port of the singlechip is respectively and electrically connected with the image processing chip and the attitude sensor, and the signal output port of the singlechip is electrically connected with the encoder.

4. A flexible wheeled leg mobile unit as claimed in claim 3, wherein: the four-bar leg mechanism also comprises a damping component, wherein the damping component comprises a sleeve, an end cover, a connecting rod and a spring; the inside of the sleeve is provided with an inner hole with one end being closed and the other end being open, the two sleeves are respectively hinged on the upper connecting rod and the driving rod at the closed ends, and the openings of the two sleeves are oppositely arranged; the two end covers are respectively and fixedly arranged at the openings of the two sleeves, and a rod penetrating hole is formed in the center of each end cover; the connecting rod comprises a small-diameter section and large-diameter sections fixedly connected to two ends of the small-diameter section, the large-diameter sections at two ends of the connecting rod are respectively in sliding fit with inner holes of the two sleeves, and two ends of the small-diameter section of the connecting rod respectively penetrate through rod penetrating holes in the two end covers; when the large-diameter section of the connecting rod moves to abut against the end face of the end cover or the closed end of the inner hole of the sleeve, the connecting rod reaches the limit position; the spring is sleeved on the small-diameter section of the connecting rod, and two ends of the spring respectively prop against the end faces of the two end covers.

5. The flexible wheeled leg mobile unit of claim 4 wherein: the battery module selects a model airplane battery, the camera selects a binocular camera, the image processing chip selects Jetson Nano edge computing development boards, the attitude sensor selects an MPU-6050 gyroscope, the encoder selects an AS5147P magnetic rotating position sensor, and the singlechip selects an ESP32 microcontroller.

6. The flexible wheeled leg mobile unit of claim 5 wherein: the wireless remote controller also comprises a wireless transmission module and a wireless remote controller; the wireless transmission module is electrically connected with the singlechip and is connected with the wireless remote controller in a wireless communication mode.

7. The flexible wheeled leg mobile unit of claim 6 wherein: the wireless transmission module is a wireless serial port module, and the wireless remote controller is a Xinjiang wireless remote controller.