Mobile carrier based on two-wheel differential drive, its control method and application

Abstract

The present invention relates to a mobile carrier based on two-wheel differential drive, which comprises a main body of the mobile carrier structure. A differential drive module and one or two wheels are installed at the bottom of the main body of the mobile carrier structure. The differential drive module includes a pair of wheel-shaped rotators, which are coaxially installed at the bottom of the main body of the mobile carrier structure. The pair of wheel-shaped rotators are respectively driven to rotate by a driving mechanism. The wheels are installed non-coaxially with the wheel-shaped rotators. The mobile carrier also includes an autonomous following electrical control module and an autonomous following ranging module. The autonomous following ranging module can measure the distance between the mobile carrier and the follower, and transmit the measured data to the autonomous following electrical control module. The autonomous following electrical control module controls the driving mechanism to work, and adjusts the rotational speeds of the pair of wheel-shaped rotators respectively through a pair of driving mechanisms to realize the following mode of the mobile carrier. The mobile carrier can also be used to realize various mobile structures. The present invention can perform multi-directional autonomous following.

Description

Technical Field

[0001] The present invention belongs to the technical field of mobile carriers, and particularly relates to a mobile carrier based on two-wheel differential drive, its control method, and application. Background Art

[0002] Three-wheel / four-wheel mobile carriers are the most common mobile carriers in industrial production, service industries, recreational places, and even in daily life, including wheelchairs, baby carriages, shopping carts, logistics transport vehicles, industrial AGVs, service robots, electronic pets, and so on. At present, the intelligent self-following of three-wheel / four-wheel mobile carriers is an important development direction. Therefore, it is imperative and of far-reaching significance to research a mobile carrier based on two-wheel differential drive, its control method, and application to meet the needs of markets such as industrial production and social services, and it has broad application prospects and high practical value. Summary of the Invention

[0003] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a mobile carrier based on two-wheel differential drive, its control method, and application to meet the needs of markets such as industrial production and social services.

[0004] The present invention solves its technical problems by adopting the following technical solutions:

[0005] The mobile carrier based on two-wheel differential drive includes a main body structure of the mobile carrier, and a differential drive module and one or two wheels are installed at the bottom of the main body structure of the mobile carrier;

[0006] The differential drive module includes a pair of wheel-shaped rotating bodies, and the pair of wheel-shaped rotating bodies are coaxially installed at the bottom of the main body structure of the mobile carrier, and the pair of wheel-shaped rotating bodies are respectively driven to rotate by a driving mechanism; one or two of the wheels are also installed at the bottom of the main body structure of the mobile carrier, and one or two of the wheels are non-coaxially installed with the wheel-shaped rotating bodies;

[0007] It further includes an autonomous following electrical control module and an autonomous following ranging module; the autonomous following ranging module can measure the distance between the mobile carrier and the follower, and transmit the measured data to the autonomous following electrical control module, and the autonomous following electrical control module controls the driving mechanism to work, and adjusts the rotation speeds of the pair of wheel-shaped rotating bodies respectively through the pair of driving mechanisms to achieve the forward, backward, turning, and stopping states of the mobile carrier, and realizes the following of the follower at any orientation position around the mobile carrier.

[0008] Further, the autonomous following electrical control module includes a power supply module, a control system, a gyroscope, and a communication module. The gyroscope is used to detect the position and motion state of the mobile carrier. The power supply module supplies power to the control system and the gyroscope through a DC-DC module. The autonomous following ranging module transmits the measured data to the control system.

[0009] Further, the autonomous following ranging module uses any one of the ranging methods such as UWB, lidar, visual image, ultrasonic radar, millimeter wave radar, and infrared radar to measure the distance between the mobile carrier and the follower.

[0010] Further, a pair of the wheel-shaped rotators adopt hub wheels, and the driving mechanism includes a pair of DC servo motors. The pair of DC servo motors are respectively connected to the pair of wheel-shaped rotators through speed reducers.

[0011] Further, a pair of the wheel-shaped rotators adopt DC servo hub motors, and the driving mechanism includes a pair of servo motor drivers. The pair of servo motor drivers drive the pair of DC servo hub motors to rotate, and can realize differential control of the two wheels by respectively changing the rotation speeds of the two DC servo hub motors.

[0012] Further, it further includes a handheld terminal. The handheld terminal moves synchronously with the follower. The handheld terminal is connected to the autonomous following electrical control module through the communication module, and can make the autonomous following electrical control module work by issuing instructions.

[0013] Further, an automatic obstacle avoidance module, a face recognition module, a smart voice module, and an alarm module are further installed on the main body of the mobile carrier structure, and the automatic obstacle avoidance module, the face recognition module, the smart voice module, and the alarm module are all circuit-connected to the control system. The automatic obstacle avoidance module can detect obstacles in front during the forward movement of the mobile carrier and make the mobile carrier stop. The face recognition module can perform face feature recognition. The smart voice module can realize voice control, voice interaction, voice recognition, and entertainment services required by the application.

[0014] The control method of the mobile carrier based on two-wheel differential drive described above includes the following steps:

[0015] Obtain the orientation and status information of the mobile carrier itself and the position information of the follower;

[0016] According to the arrangement of the autonomous following ranging module and the selection of the autonomous following control quantity based on ranging, the following control quantity is determined according to the control algorithm. The forward, backward, turning, and stopping states of the mobile carrier are realized by adjusting the rotational speeds of a pair of wheel-shaped rotators through a pair of driving mechanisms, so as to realize the following of the followed object at any orientation position around the mobile carrier.

[0017] The application of the mobile carrier based on two-wheel differential drive described above: various wheeled mobile devices with the mobile carrier as the basic two-wheel differential drive mode.

[0018] Among them, the wheeled mobile device is any one of a wheelchair, a baby carriage, a pet carriage, a shopping cart, a luggage cart, a mobile service robot, and a mobile suitcase.

[0019] The advantages and positive effects of the present invention are:

[0020] 1. In the present invention, a pair of driving mechanisms are respectively used to drive a pair of wheel-shaped rotators. By respectively changing the rotational speeds of the two wheel-shaped rotators, speed control can be realized, and differential control of the two wheel-shaped rotators can also be realized, so as to realize the forward, backward, turning, and stopping of the mobile carrier.

[0021] 2. In the present invention, the autonomous following ranging module can measure the distance between the mobile carrier and the followed object and transmit the measured data to the autonomous following electrical control module. The autonomous following electrical control module realizes the differential control of the two wheels by respectively changing the rotational speeds of the wheel-shaped rotators, so as to achieve synchronous following of the followed object.

[0022] 3. In the present invention, a pair of driving mechanisms are respectively used to adjust the rotational speeds of a pair of wheel-shaped rotators to realize the forward, backward, turning, and stopping states of the mobile carrier, and realize the following of a person at any orientation position around the mobile carrier; among them, the following control component is determined according to the arrangement scheme of the autonomous following ranging module and the selection of the autonomous following control quantity based on ranging, according to the existing control algorithm, so as to realize the multi-directional autonomous following of the mobile carrier. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The technical solution of the present invention will be further described in detail below with reference to the drawings and embodiments. However, it should be understood that these drawings are only designed for the purpose of explanation and therefore do not limit the scope of the present invention. In addition, unless otherwise specified, these drawings are only intended to conceptually illustrate the structural configuration described herein and are not necessarily drawn to scale.

[0024] Figure 1 It is a schematic structural diagram of the mobile carrier based on two-wheel differential drive provided in Embodiment 1 of the present invention;

[0025] Figure 2Schematic diagram of the drive mechanism of the mobile carrier based on two-wheel differential drive and the connection structure of the wheel-shaped rotating body provided in Embodiment 1 of the present invention;

[0026] Figure 3 Schematic diagram of the structure of the mobile carrier based on two-wheel differential drive provided in Embodiment 2 of the present invention;

[0027] Figure 4 Schematic diagram of the drive mechanism of the mobile carrier based on two-wheel differential drive and the connection structure of the wheel-shaped rotating body provided in Embodiment 2 of the present invention;

[0028] Figure 5 Schematic diagram of the layout structure of the autonomous following ranging module of the mobile carrier based on two-wheel differential drive provided in Embodiment 1 or 2 of the present invention;

[0029] Figure 6 Schematic diagram of the electrical connection of the mobile carrier based on two-wheel differential drive provided in Embodiment 1 or 2 of the present invention;

[0030] Note: Figure 6 All the connections in represent only the association of a certain communication method or the association between components, rather than the actual circuit connection lines; Detailed implementation mode

[0031] First of all, it should be noted that the following will specifically illustrate the specific structure, characteristics and advantages of the present invention by way of examples. However, all the descriptions are only for the purpose of explanation and should not be construed as any limitation to the present invention. In addition, any single technical feature described or implied in each embodiment mentioned in this article, or any single technical feature shown or implied in each drawing, can still be arbitrarily combined or deleted between these technical features (or their equivalents) to obtain more other embodiments of the present invention that may not be directly mentioned in this article. In addition, for the sake of simplifying the drawings, the same or similar technical features may only be marked in one place in the same drawing.

[0032] Embodiment 1

[0033] As Figure 1 , 2 , the mobile carrier based on two-wheel differential drive provided in this embodiment includes the main body 1 of the mobile carrier structure. A differential drive module and a wheel 2 are installed at the bottom of the main body 1 of the mobile carrier structure. It should be noted that, for greater flexibility, it can be considered that the wheel 2 is a universal wheel;

[0034] The differential drive module includes a pair of wheel-shaped rotators coaxially installed at the bottom of the main body of the mobile carrier structure. The pair of wheel-shaped rotators are respectively driven to rotate by drive mechanisms. Specifically, the first drive mechanism drives the first wheel-shaped rotator, and the second drive mechanism drives the second wheel-shaped rotator. One wheel 2 is also installed at the bottom of the main body of the mobile carrier structure, and one wheel 2 is installed non-coaxially with the wheel-shaped rotator.

[0035] The pair of wheel-shaped rotators adopt hub wheels. The drive mechanism includes a pair of DC servo motors, and the pair of DC servo motors are respectively connected to the pair of wheel-shaped rotators through speed reducers. In this embodiment, the pair of wheel-shaped rotators are respectively the first hub wheel 3 and the second hub wheel 5. The first hub wheel 3 and the second hub wheel 5 are respectively driven by the first servo motor 18 and the second servo motor 14. Specifically, the first servo motor 18 and the second servo motor 14 are respectively assembled with the first speed reducer and the second speed reducer. The output shafts of the first speed reducer and the second speed reducer are respectively assembled with the first hub wheel 3 and the second hub wheel 5 of the mobile carrier through the first coupling 15 and the second coupling 12. It should be noted that the first servo motor 18 and the second servo motor 14 are respectively fixed on the first motor connection plate 17 and the second motor connection plate 13 on both sides of the electric control box 4, and the electric control box 4 is fixedly installed at the bottom of the main body 1 of the mobile carrier structure. By adjusting the rotation speeds of the first servo motor 18 and the second servo motor 14, functions such as the mobile carrier moving forward, backward, turning, and stopping can be realized.

[0036] In addition, it can also be considered that the pair of wheel-shaped rotators adopt DC servo hub motors. The drive mechanism includes a pair of servo motor drivers, and the pair of servo motor drivers drive the pair of DC servo hub motors to rotate and can realize differential control of the two wheels by respectively changing the rotation speeds of the two DC servo hub motors. This method can also realize the differential rotation of the wheel-shaped rotators. The specific installation structure can be installed by those skilled in the art according to specific situations and will not be elaborated here.

[0037] It also includes an autonomous following electrical control module and an autonomous following ranging module. The autonomous following ranging module can measure the distance between the mobile carrier and the follower and transmit the measured data to the autonomous following electrical control module. The autonomous following electrical control module controls the drive mechanism to work, and realizes the forward, backward, turning, and stopping states of the mobile carrier by respectively adjusting the rotation speeds of the pair of wheel-shaped rotators through the pair of drive mechanisms, so as to realize following the follower at any orientation position around the mobile carrier.

[0038] Specifically, the autonomous following electrical control module includes a power supply module, a control system, a gyroscope, and a communication module. The gyroscope is used to detect the position and motion state of the mobile carrier and transmit the detected information to the control system, enabling the translational mobile carrier to achieve balance during forward movement. The power supply module powers the control system and the gyroscope through a DC-DC module. The autonomous following ranging module transmits the measured data to the control system through the communication module. Among them, the autonomous following electrical control module can be installed in the electric control box 4.

[0039] The control system adopts any one of STM32, Raspberry Pi, 51 series single-chip microcomputers, and small industrial computers.

[0040] The autonomous following ranging module uses any one of UWB, lidar, visual image, ultrasonic radar, millimeter wave radar, and infrared radar ranging methods to measure the distance between the mobile carrier and the follower. In this embodiment, the UWB technology is used to achieve distance measurement. Specifically, the autonomous following ranging module includes two UWB base stations and one UWB tag. The two UWB base stations are installed at asymmetric positions on the main body of the mobile carrier structure. The UWB tag is installed on the handheld terminal. The handheld terminal moves synchronously with the follower. The handheld terminal is connected to the autonomous following electrical control module through the communication module, so that the distances between the UWB tag and the two UWB base stations can be sent to the autonomous following electrical control module, and the autonomous following electrical control module can be made to work by issuing commands.

[0041] Specifically, a Bluetooth wireless module can be built into the handheld terminal for communication with the autonomous following electrical control module. Front, rear, left, and right following setting buttons, as well as a hand-push assist mode and a stop button, can also be provided on the terminal panel of the handheld terminal. The specific setting method is well-known to those skilled in the art and will not be elaborated here.

[0042] To expand the various functions of the mobile carrier, the following can also be considered: An automatic obstacle avoidance module, a face recognition module, an intelligent voice module, and an alarm module are also installed on the main body of the mobile carrier structure; the automatic obstacle avoidance module, the face recognition module, the intelligent voice module, and the alarm module are all connected to the control system circuit in the autonomous following electrical control module, and the operation of the automatic obstacle avoidance module, the face recognition module, the intelligent voice module, and the alarm module is controlled through the control system; the automatic obstacle avoidance module can detect obstacles in front during the forward movement of the mobile carrier and cause the mobile carrier to stop; specifically, the automatic obstacle avoidance module is not limited to using technologies such as ultrasonic technology, infrared technology, machine vision (such as cameras) to detect obstacles. For example, a camera is installed at the front position of the main body of the mobile carrier structure, and the camera captures the scene in the forward direction of the mobile carrier and transmits the acquired data to the autonomous following electrical control module. When the autonomous following electrical control module detects an obstacle in front, the wheels are controlled to stop moving through the autonomous following electrical control module; the face recognition module can also perform face feature recognition by using a camera to meet on-site applications; the intelligent voice module can be based on iFlytek voice technology and use existing iFlytek integrated modules to achieve voice control, voice interaction, and voice recognition functions required by the application, and can also provide service items such as music playing, story playing, and online courses; when the automatic obstacle avoidance module detects an obstacle, an alarm can be issued through the alarm module, or when the face recognition module recognizes a stranger approaching, an alarm can also be issued through the alarm module.

[0043] It should be noted that in this embodiment, the algorithm design of the differential following controller in the control system is as follows:

[0044] This embodiment takes left-side following as an example to illustrate the design of the side following controller, as Figure 5 shown. A coordinate system O-xy is established with the center of the mobile carrier as the origin; it is stipulated that the negative direction of the x-axis is forward, the positive direction of the x-axis is backward, the negative direction of the y-axis is left, and the positive direction of the y-axis is right; assume that two UWB base stations are respectively placed at points A and B, and A' and B' are the other two endpoints of the rectangle with A and B as the diagonal. When the UWB tag is at point C, it is the equilibrium position, that is, e h = 0, e l = 0. Then, according to the lengths of the three sides of the measured triangle ACB, it is very easy to obtain using the cosine theorem:

[0045]

[0046] So

[0047] l BD = l BC cos∠CBA′ (Equation 2)

[0048] Assume that the UWB tag 21 is fixed on the person being followed and moves in real time as the person being followed moves. When the UWB tag 21 moves to point C’, the lengths of the three sides of triangle AC’B can be obtained respectively. It is easy to get by using the cosine theorem:

[0049]

[0050] Then

[0051] l BD′ = l BC′ cos∠C′BA′ (Equation 4)

[0052] Then

[0053] e l = l BD′ - l BD (Equation 5)

[0054] Similarly

[0055] e h = l C′D′ - l CD (Equation 6)

[0056] When the UWB tag 21 moves to point C’, the displacement amounts generated in the xy directions relative to point C are e l 、e h respectively. PID controllers are constructed respectively

[0057]

[0058]

[0059] Among them, u x is the control amount to make the mobile carrier follow forward, and u y is the differential control amount applied to the left and right rear wheels to make the mobile carrier maintain the side distance from the person being followed. Assume that the moving speed of the mobile carrier at the current moment is v0 (which can be measured by the built-in encoder of the servo motor). K p 、K d 、K i are the proportional coefficient, differential coefficient, and integral coefficient of the PID controller respectively. The superscripts x and y represent their coefficients in the x and y directions. Then, the speeds applied to the left and right rear wheels are

[0060]

[0061]

[0062] And so on, it is easy to design the controller for following the right side;

[0063] This embodiment takes the front - side following as an example to illustrate the design of the front - and - rear following controller. As Figure 5 shown, a coordinate system O - xy is established with the center of the mobile carrier as the origin; it is stipulated that the negative x - axis direction is the front, the positive x - axis direction is the rear, the negative y - axis direction is the left, and the positive y - axis direction is the right; when the UWB tag 21 is at point F, it is in the equilibrium position, that is, e fh = 0, e fl = 0. Assume that the UWB tag 21 is fixed on the followed object and moves in real - time as the followed object moves. When the UWB tag 21 moves to point F', it is easy to obtain the values of e fh and e fl . Then, when the UWB tag 21 moves to point F', the displacement amounts generated in the xy - directions relative to point F are e fl and e fh respectively. PID controllers are constructed respectively:

[0064]

[0065]

[0066] where μ x is the control quantity for the mobile carrier to follow forward, μ y is the differential speed control quantity applied to the left and right rear wheels for the mobile carrier to maintain the left - right deviation from the followed object. Assume that the current moving speed of the mobile carrier is v0 (which can be measured by the built - in encoder of the DC servo motor), k p , k d , and k i are the proportional coefficient, differential coefficient, and integral coefficient of the PID controller respectively. The superscripts x and y represent their coefficients in the x and y directions. Then, the speeds applied to the left and right rear wheels are:

[0067]

[0068]

[0069] And so on, it is easy to design the controller for the rear - side following.

[0070] It should be noted that l MN is the distance between points M and N;

[0071] It should be noted that the algorithm design of the differential - following controller in the control system can adopt the above - mentioned PID control algorithm, and can also adopt existing control algorithms such as optimal control, active disturbance rejection control, adaptive control, sliding - mode control, bang - bang control, robust control, etc. The specific design algorithms will not be elaborated one by one.

[0072] Embodiment 2

[0073] As Figure 3 、 4 shown in, the mobile carrier based on two-wheel differential drive provided in this embodiment includes a main body 6 of the mobile carrier structure. A differential drive module and two wheels are installed at the bottom of the main body 6 of the mobile carrier structure. As Figure 3 shown in, the two wheels are a first wheel 7 and a second wheel 8 respectively. It should be noted that, for greater flexibility, it can be considered that both the first wheel 7 and the second wheel 8 are universal wheels;

[0074] The differential drive module includes a pair of wheel-shaped rotating bodies. The pair of wheel-shaped rotating bodies are coaxially installed at the bottom of the main body of the mobile carrier. The pair of wheel-shaped rotating bodies are respectively driven to rotate by a drive mechanism. Specifically, a first drive mechanism drives the first wheel-shaped rotating body, and a second drive mechanism drives the second wheel-shaped rotating body; the two wheels are also installed at the bottom of the main body of the mobile carrier, and the two wheels are non-coaxially installed with the wheel-shaped rotating bodies;

[0075] The pair of wheel-shaped rotating bodies adopt hub wheels. The drive mechanism includes a pair of DC servo motors. The pair of DC servo motors are respectively connected to the pair of wheel-shaped rotating bodies through speed reducers; in this embodiment, the pair of wheel-shaped rotating bodies are a first hub wheel 9 and a second hub wheel 11 respectively. The first hub wheel 9 and the second hub wheel 11 are respectively driven by a first servo motor 18 and a second servo motor 14. Specifically, the first servo motor 18 and the second servo motor 14 are respectively assembled with a first speed reducer and a second speed reducer. The output shafts of the first speed reducer and the second speed reducer are respectively assembled with the first hub wheel 9 and the second hub wheel 11 of the mobile carrier through a first coupling 15 and a second coupling 12. It should be noted that the first servo motor 18 and the second servo motor 14 are respectively fixed on the first motor connection plate 17 and the second motor connection plate 13 on both sides of the electric control box 10, and the electric control box 10 is fixedly installed at the bottom of the main body 6 of the mobile carrier; by adjusting the rotation speeds of the first servo motor 18 and the second servo motor 14, functions such as the mobile carrier moving forward, backward, turning, and stopping are realized;

[0076] In addition, it can also be considered that: the pair of wheel-shaped rotating bodies adopt DC servo hub motors. The drive mechanism includes a pair of servo motor drivers. The pair of servo motor drivers drive the pair of DC servo hub motors to rotate, and can realize the differential control of the two wheels by respectively changing the rotation speeds of the two DC servo hub motors; this method can also realize the differential rotation of the wheel-shaped rotating bodies. The specific installation structure can be specifically installed by those skilled in the art according to the specific situation, and will not be elaborated here.

[0077] It further includes an autonomous following electric control module and an autonomous following ranging module; the autonomous following ranging module can measure the distance between the mobile carrier and the follower, and transmit the measured data to the autonomous following electric control module, and the autonomous following electric control module controls the driving mechanism to work, and adjusts the rotation speeds of a pair of wheel-shaped rotators through a pair of the driving mechanisms respectively to realize the forward, backward, turning and stopping states of the mobile carrier, so as to realize the following of the follower at any orientation position around the mobile carrier.

[0078] Specifically, the autonomous following electric control module includes a power supply module, a control system, a gyroscope and a communication module. The gyroscope is used to detect the position and motion state of the mobile carrier, and transmit the detected information to the control system, so that the mobile carrier can achieve balance during the forward movement; the power supply module supplies power to the control system and the gyroscope through a DC-DC module, and the autonomous following ranging module transmits the measured data to the control system through the communication module. Among them, the autonomous following electric control module can be installed in the electric control box 10.

[0079] The control system adopts any one of STM32, Raspberry Pi, 51 series single-chip microcomputers and small industrial computers.

[0080] The autonomous following ranging module adopts any one of ranging methods such as UWB, lidar, visual image, ultrasonic radar, millimeter wave radar and infrared radar to measure the distance between the mobile carrier and the follower; in this embodiment, the UWB technology is adopted to realize the distance measurement. Specifically: the autonomous following ranging module includes two UWB base stations and one UWB tag. The two UWB base stations are installed at asymmetric positions on the main body structure of the mobile carrier, and the UWB tag is installed on the handheld terminal. The handheld terminal moves synchronously with the follower, and the handheld terminal is connected to the autonomous following electric control module through the communication module, so that the distances between the UWB tag and the two UWB base stations can be sent to the autonomous following electric control module, and the autonomous following electric control module can be made to work by issuing instructions. Specifically, in this embodiment, as Figure 5 , the two UWB base stations are respectively the first UWB base station 19 and the second UWB base station 20, and the first UWB base station 19 and the second UWB base station 20 are respectively installed at two obviously axis-asymmetric positions on the mobile carrier frame. Figure 5 In

[0081] Specifically, a Bluetooth wireless module can be built into the handheld terminal for communication with the autonomous following electrical control module. Front, rear, left, and right following setting buttons, as well as a hand-push assist mode and a parking button, can also be provided on the terminal panel of the handheld terminal. The specific setting method is well-known to those skilled in the art and will not be elaborated here.

[0082] To expand the various functions of the mobile carrier, the following can also be considered: An automatic obstacle avoidance module, a face recognition module, a smart voice module, and an alarm module are also installed on the main body of the mobile carrier structure. The automatic obstacle avoidance module, the face recognition module, the smart voice module, and the alarm module are all electrically connected to the control system in the autonomous following electrical control module, and the operation of the automatic obstacle avoidance module, the face recognition module, the smart voice module, and the alarm module is controlled through the control system. The automatic obstacle avoidance module can detect obstacles in front during the forward movement of the mobile carrier and cause the mobile carrier to stop. Specifically, the automatic obstacle avoidance module is not limited to using technologies such as ultrasonic technology, infrared technology, machine vision (such as a camera) to detect obstacles. For example, a camera is installed at the front position of the main body of the mobile carrier structure. The camera captures the scene in the forward direction of the mobile carrier and transmits the acquired data to the autonomous following electrical control module. When the autonomous following electrical control module detects an obstacle in front, it controls the wheels to stop moving through the autonomous following electrical control module. The face recognition module can also perform face feature recognition by using a camera to meet on-site applications. The smart voice module can be based on iFlytek voice technology and use existing iFlytek integrated modules to implement voice control, voice interaction, and voice recognition functions required by the application, and can also provide service items such as music playback, story playback, and online courses. When the automatic obstacle avoidance module detects an obstacle, it can alarm through the alarm module, or when the face recognition module recognizes a stranger approaching, it can also alarm through the alarm module.

[0083] It should be noted that in this embodiment, the algorithm design of the differential following controller in the control system is as follows:

[0084] This embodiment takes left-side following as an example to illustrate the design of the side following controller. As Figure 5 shown, a coordinate system O-xy is established with the center of the mobile carrier as the origin. It is stipulated that the negative direction of the x-axis is the front, the positive direction of the x-axis is the rear, the negative direction of the y-axis is the left, and the positive direction of the y-axis is the right. Assume that two UWB base stations are respectively placed at points A and B, and A' and B' are the other two endpoints of the rectangle with A and B as the diagonal. When the UWB tag is at point C, it is the equilibrium position, that is, e h = 0, e l = 0. Then, according to the lengths of the three sides of the measured triangle ACB, it is very easy to obtain using the cosine theorem:

[0085]

[0086] Then

[0087] l BD = l BC cos∠CBA′ (Equation 2)

[0088] Assume that the UWB tag 21 is fixed on the person being followed and moves in real time as the person being followed moves. When the UWB tag 21 moves to point C′, the lengths of the three sides of triangle AC′B can be obtained respectively. Using the cosine theorem, it is easy to get:

[0089]

[0090] Then

[0091] l BD′ = l BC′ cos∠C′BA′ (Equation 4)

[0092] Then

[0093] e l = l BD′ - l BD (Equation 5)

[0094] Similarly

[0095] e h = l C′D′ - l CD (Equation 6)

[0096] When the UWB tag 21 moves to point C′, the displacement amounts in the xy directions relative to point C are e l and e h respectively. PID controllers are constructed respectively

[0097]

[0098]

[0099] Among them, u x is the control amount to make the mobile carrier follow forward, and u y is the differential control amount applied to the left and right rear wheels to make the mobile carrier maintain the side distance from the person being followed. Assume that the moving speed of the mobile carrier at the current moment is v0 (which can be measured by the built-in encoder of the servo motor). K p , K d , K i are the proportional coefficient, differential coefficient, and integral coefficient of the PID controller respectively. The superscripts x and y represent their coefficients in the x and y directions. Then, the speeds applied to the left and right rear wheels are

[0100]

[0101]

[0102] And so on, it is easy to design a controller for the right-side following;

[0103] This embodiment takes the front-side following as an example to illustrate the design of the front-and-back following controller. As Figure 5 shown, a coordinate system O-xy is established with the center of the mobile carrier as the origin; it is stipulated that the negative direction of the x-axis is the front, the positive direction of the x-axis is the back, the negative direction of the y-axis is the left, and the positive direction of the y-axis is the right; when the UWB tag 21 is located at point F, it is the equilibrium position, that is, e fh =0, e fl =0. Assume that the UWB tag 21 is fixed on the followed object and moves in real time as the followed object moves. When the UWB tag 21 moves to point F', it is easy to obtain the values of e fh and e fl . Then, when the UWB tag 21 moves to point F', the displacement amounts generated in the xy directions relative to point F are e fl and e fh respectively. PID controllers are constructed respectively:

[0104]

[0105]

[0106] Among them, μ x is the control amount for the mobile carrier to follow forward, and μ y is the differential control amount for the left and right rear wheels of the mobile carrier to maintain the left-right deviation from the followed object. Assume that the current moving speed of the mobile carrier is v0 (which can be measured by the built-in encoder of the DC servo motor). k p , k d , and k i are the proportional coefficient, differential coefficient, and integral coefficient of the PID controller respectively. The superscripts x and y represent their coefficients in the x and y directions. Then, the speeds applied to the left and right rear wheels are:

[0107]

[0108]

[0109] And so on, it is easy to design a controller for the back-side following.

[0110] It should be noted that l MN is the distance between points M and N;

[0111] It should be noted that the algorithm design of the differential following controller in the control system can adopt the above PID control algorithm, and can also adopt existing control algorithms such as optimal control, auto-disturbance rejection control, adaptive control, sliding mode control, bang-bang control, and robust control. The specific design algorithms will not be elaborated one by one.

[0112] Embodiment 3

[0113] The control method of the mobile carrier based on two-wheel differential drive in Embodiment 1 and Embodiment 2 includes the following steps:

[0114] Obtain the orientation and state information of the mobile carrier itself and the position information of the follower.

[0115] According to the layout of the autonomous following ranging module and the selection of the autonomous following control quantity based on ranging, determine the following control quantity according to the control algorithm, and adjust the rotation speeds of a pair of wheel-shaped rotating bodies through a pair of driving mechanisms respectively to realize the forward, backward, turning, and stopping states of the mobile carrier, so as to realize the following of the follower at any orientation position around the mobile carrier.

[0116] It should be noted that the control algorithm can adopt the PID control algorithm in Embodiments 1 and 2, and can also adopt existing control algorithms such as optimal control, auto-disturbance rejection control, adaptive control, sliding mode control, bang-bang control, and robust control. The specific design algorithms will not be elaborated one by one.

[0117] Embodiment 4

[0118] The application of the mobile carrier based on two-wheel differential drive described in Embodiments 1 and 2: various wheeled mobile devices with the basic two-wheel differential drive mode of the mobile carrier; wherein, the wheeled mobile device is any one of a wheelchair, a baby carriage, a pet carriage, a shopping cart, a luggage cart, a mobile service robot, and a mobile suitcase.

[0119] Specifically, by adding corresponding structures to the surface of the mobile carrier based on two-wheel differential drive, a wheelchair, a pet carriage, a shopping cart, a luggage cart, a mobile service robot, and a mobile suitcase can be obtained. The specific structures to be added can be added according to actual needs, and the specific structures can be designed by oneself.

[0120] The above embodiments have described the present invention in detail, but the content described is only the preferred embodiment of the present invention and cannot be considered as limiting the scope of implementation of the present invention. All equivalent changes and improvements made according to the scope of the application of the present invention should still fall within the scope covered by the patent of the present invention.

Claims

1. Control method for a mobile carrier based on two-wheel differential drive, characterized in that: The mobile carrier based on two-wheel differential drive includes a main body of the mobile carrier structure, and a differential drive module and one or two wheels are installed at the bottom of the main body of the mobile carrier structure; The differential drive module includes a pair of wheel-shaped rotators. The pair of wheel-shaped rotators are coaxially installed at the bottom of the main body of the mobile carrier structure, and the pair of wheel-shaped rotators are respectively driven to rotate by a drive mechanism; one or two of the wheels are also installed at the bottom of the main body of the mobile carrier structure, and one or two of the wheels are installed non-coaxially with the wheel-shaped rotators; It further includes an autonomous following electrical control module and an autonomous following ranging module; the autonomous following ranging module can measure the distance between the mobile carrier and the follower, and transmit the measured data to the autonomous following electrical control module. The autonomous following electrical control module controls the drive mechanism to work, and adjusts the rotation speeds of the pair of wheel-shaped rotators through the pair of drive mechanisms respectively to achieve the forward, backward, turning, and stopping states of the mobile carrier, so as to achieve following of the follower at any orientation position around the mobile carrier; The autonomous following ranging module includes two UWB base stations and one UWB tag. The two UWB base stations are installed at asymmetric positions on the main body of the mobile carrier structure. The UWB tag is installed on the handheld terminal. The handheld terminal moves synchronously with the follower. The handheld terminal is connected to the autonomous following electrical control module through a communication module, so that the distances between the UWB tag and the two UWB base stations can be sent to the autonomous following electrical control module, and the autonomous following electrical control module can be made to work by issuing commands; The control method includes the following steps: Obtain the orientation and status information of the mobile carrier itself and the position information of the follower; According to the layout of the autonomous following ranging module and the selection of the autonomous following control quantity based on ranging, determine the following control quantity according to the control algorithm, and adjust the rotation speeds of the pair of wheel-shaped rotators through the pair of drive mechanisms respectively to achieve the forward, backward, turning, and stopping states of the mobile carrier, so as to achieve following of the follower at any orientation position around the mobile carrier; When the follower is being followed around the mobile carrier, The design method of the left-side following controller is: Establish a coordinate system O-xy with the center of the mobile carrier as the origin; stipulate that the negative direction of the x-axis is the front, the positive direction of the x-axis is the rear, the negative direction of the y-axis is the left, and the positive direction of the y-axis is the right; assume that two UWB base stations are placed at points A and B respectively, and A' and B' are the other two endpoints of the rectangle with A and B as the diagonals. Let the UWB tag be at point C on the positive left side of the mobile carrier, which is the equilibrium position, i.e., e h = 0, e l = 0. Then, according to the lengths of the three sides of triangle ACB measured, it is very easy to obtain using the cosine theorem: So l BD = l BC cos∠CBA′ (Equation 2) Assume that the UWB tag is fixed on the follower and moves in real time as the follower moves. When the UWB tag moves to point C’, the lengths of the three sides of triangle AC’B can be obtained respectively. It is easy to obtain by using the cosine theorem: So l BD′ = l BC′ cos∠C′BA′ (Equation 4) Then e l = l BD′ - l BD (Equation 5) Similarly e h = l C′D′ -l CD (Equation 6) When the UWB tag moves to point C', the displacement amounts generated relative to point C in the xy directions are e l and e h respectively, and PID controllers are constructed respectively where, u x is the control quantity for the mobile carrier to follow forward, and u y is the differential control quantity applied to the left and right rear wheels for the mobile carrier to maintain the lateral distance from the object being followed. Assuming that the current moving speed of the mobile carrier is v0, K p , K d , and K i are the proportional coefficient, differential coefficient, and integral coefficient of the PID controller respectively. Their superscripts x and y represent their coefficients in the x and y directions. Then, the speeds applied to the left and right rear wheels are By analogy, the design method of the right-side following controller is obtained; The design method of the front-side following controller is: A coordinate system O-xy is established with the center of the mobile carrier as the origin; it is stipulated that the negative direction of the x-axis is the front, the positive direction of the x-axis is the rear, the negative direction of the y-axis is the left, and the positive direction of the y-axis is the right; when the UWB tag is located at point F directly in front of the mobile carrier, it is the equilibrium position, i.e., e fh = 0, e fl = 0. Assume that the UWB tag is fixed on the person being followed and moves in real time as the person being followed moves. When the UWB tag moves to point F', it is easy to obtain the values of e fh and e fl . Then, when the UWB tag moves to point F', the displacement amounts relative to point F in the xy directions are e fl and e fh respectively. PID controllers are constructed respectively: where, μ x is the control quantity for the mobile carrier to follow forward, μ y is the differential control quantity applied to the left and right rear wheels for the mobile carrier to maintain the left and right deviations from the followed object. Assume that the moving speed of the mobile carrier at the current moment is v0, k p 、k d 、k i are the proportional coefficient, differential coefficient, and integral coefficient of the PID controller respectively. Their superscripts x and y represent their coefficients in the x and y directions. Then, the speeds applied to the left and right rear wheels are: By analogy, the design method of the rear-side following controller is obtained.

2. The control method for a mobile carrier based on two-wheel differential drive according to claim 1, characterized in that: The autonomous following electrical control module includes a power supply module, a control system, a gyroscope, and a communication module. The gyroscope is used to detect the position and motion state of the mobile carrier; the power supply module supplies power to the control system and the gyroscope through a DC-DC module, and the autonomous following ranging module transmits the measured data to the control system.

3. The control method for a mobile carrier based on two-wheel differential drive according to claim 1, characterized in that: One pair of the wheel-shaped rotators adopts hub wheels, and the driving mechanism includes a pair of DC servo motors, and the pair of DC servo motors are respectively connected to the pair of wheel-shaped rotators through speed reducers.

4. The control method of a mobile carrier based on two-wheel differential drive according to claim 1, wherein: One pair of the wheel-shaped rotators adopts DC servo hub motors, and the driving mechanism includes a pair of servo motor drivers. The pair of servo motor drivers drive the pair of DC servo hub motors to rotate, and can realize differential control of the two wheels by respectively changing the rotational speeds of the two DC servo hub motors.

5. The control method of a mobile carrier based on two-wheel differential drive according to claim 2, wherein: An automatic obstacle avoidance module, a face recognition module, a smart voice module, and an alarm module are further installed on the main body of the mobile carrier structure, and the automatic obstacle avoidance module, the face recognition module, the smart voice module, and the alarm module are all circuit-connected to the control system; the automatic obstacle avoidance module can detect obstacles in front during the forward movement of the mobile carrier and cause the mobile carrier to stop; the face recognition module can perform face feature recognition; the smart voice module can realize voice control, voice interaction, voice recognition, and entertainment services required by the application, and the control system controls the alarm module to give an alarm.

6. The application of the control method of a mobile carrier based on two-wheel differential drive according to any one of claims 1-5, wherein: A variety of wheeled mobile devices with the control method of the mobile carrier being a two-wheel differential drive control method.

7. The application of the control method of a mobile carrier based on two-wheel differential drive according to claim 6, wherein: The wheeled mobile device is any one of a wheelchair, a baby carriage, a pet carriage, a shopping cart, a luggage cart, a mobile service robot, and a mobile suitcase.

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