Active hopping wheel-legged balancing robot and control method thereof

Abstract

The application discloses a wheel-leg balance robot design capable of active jumping and a control method thereof. The wheel-leg balance robot design is based on a planar parallel five-bar mechanism, and comprehensively considers the leg structure design and wheel train structure design of the wheel-leg balance robot suitable for active jumping. A plurality of sensor modules are adopted for sensing, so that the robot can autonomously perform the jumping function on a complex obstacle road section. Meanwhile, the wheel diameter and the motor torque are matched and designed, so that the robot has strong passability. The joint motor connection structure is improved to improve the design strength of the leg structure. An inverted pendulum model containing a wheel-leg hybrid structure is used to fit the robot movement, an LQR control algorithm is adopted to process the nonlinear system through piecewise linearization, and reference input is added to realize trajectory tracking.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of wheel-legged robots, and relates to a wheel-legged balancing robot capable of active jumping and a control method thereof. BACKGROUND

[0002] Mobile robots are becoming more and more mature in types and styles, and can be roughly divided into two categories: one is a foot-type walking robot, and the other is a wheel-type mobile robot. The foot-type walking robot has advantages such as anti-terrain interference and strong adaptability, but because of the complexity of dynamic stability control, the moving speed and practical application of the foot-type walking robot are limited, and the foot-type walking robot cannot pass through obstacles such as steps quickly. The wheel-type mobile robot has advantages such as fast moving speed and convenient load carrying, but because of the limitation of the wheel structure, the wheel-type mobile robot is more suitable for moving on flat ground and has no solution to complex gradient terrains. Therefore, on this basis, the foot-wheel robot that combines the functions of the above two types of robots has been widely concerned. By combining the wheel structure of the wheel-type mobile robot with the foot mechanism of the foot-type walking robot, the robot can have a high moving speed and can move stably on complex terrain.

[0003] At present, many domestic and foreign universities and research institutions are conducting research on wheel-legged robots. After years of development, although the research on the double-foot wheel robot has made a series of progress, there is still a certain distance from practical application. The double-foot wheel robot is a kind of multi-modal composite robot, and the main reason restricting the development of the double-foot wheel robot is that the performance of the system design and motion control cannot meet the demand of practical application, especially the balance stability control of the robot. The double-foot wheel robot is a natural unstable system, and it needs to continuously exert control to maintain its own balance and stability during work. How the robot maintains its own balance and stability while performing work tasks and resisting external disturbances is a key technology, and how to ensure fast movement on complex terrain and gradient road surface is the main problem of the present application.

[0004] The patent application with the publication number CN 118579172 A discloses a symmetrical five-link closed-chain double-wheel-legged robot and a motion control method thereof. The robot has a five-link closed-chain coupling driving wheel structure on one side, and adopts a left-right and front-back symmetrical body structure distribution. The robot has a six-degree-of-freedom structure design, three degrees of freedom on each of the left and right sides, respectively, to control the pitch of the body, the extension and contraction of the leg link, and the rolling of the driving wheel. The dynamic balance control of the robot is completed through the cooperation of the hip joint motor and the wheel motor, the fast wheeled movement on the flat ground is realized, and when obstacles are encountered, the take-off jumping movement is realized through the energy storage and extension action of the thigh link and the calf link. However, the technical solution does not involve the design of the wheel train, the design of the controller, and other design contents related to the fast and smooth movement of the robot on complex terrain and roads with gradients. SUMMARY

[0005] Due to the above-mentioned defects of the prior art, the present application provides a wheel-legged balancing robot design and control method that can actively jump, making the robot's leg structure stronger and having stronger passability, and being able to autonomously jump on complex obstacle sections.

[0006] To achieve the above-mentioned purpose, in a first aspect, the present application provides a wheel-legged balancing robot design that can actively jump, including a chassis, leg link structures on the left and right sides thereof, a wheel set at the bottom of the leg link structure, power hardware and control hardware connected to the chassis;

[0007] The leg link structure is a planar parallel five-bar mechanism, including a rack fixed to the chassis, two thighs arranged on the outer side of the rack, and a front calf and a rear calf rotatably connected to the thighs. The front calf is installed with a hub motor stator at the bottom, and the rear calf is connected through a flange shaft at the corresponding position at the bottom, forming a rotating pair. In order to provide support for the robot after power failure and falling to the ground, the robot tilt angle that can be obtained by the joint motor encoder after power-on is set, and a pair of guide wheels is arranged on the front and rear sides of the chassis, with a laser ranging module at the bottom of the front part and a positioning module inside.

[0008] The thigh is connected to the rotor of the joint motor through the joint motor connecting piece of the rack; the stator of the joint motor is fixedly connected to the chassis through a fixed plate; the thigh connected to the front calf is raised by a pad to provide the required vertical distance for the calf connection without interference; a leg limiting block is arranged at the connection between the thigh and the rack, and a limiting pad is installed at the thigh connected to the front calf to compensate for the limiting function, so as to ensure the determination of the leg posture of the robot after power-on again and not to lose zero position.

[0009] The wheel diameter range is determined based on the initial speed and power requirements for overtaking and the characteristic parameters of the hub motor to achieve a match;

[0010] The control hardware consists of two microcontrollers, and two central boards are set up to distribute the power to the circuit.

[0011] The design of the wheel-legged balancing robot comprehensively considers the leg structure and wheel system design suitable for active jumping, and uses multiple sensor modules for perception, enabling the robot to autonomously jump over complex obstacle courses; at the same time, the wheel diameter and motor torque are matched to give the robot strong passability.

[0012] Furthermore, the main structure of the chassis includes a "well"-shaped frame composed of horizontal and vertical aluminum squares, and the robot circuit is covered and shielded with sheet metal. Fixed aluminum squares and hardware mounting plates are fixedly connected to the "well"-shaped frame. The robot chassis is connected to the frame through a horizontal baffle to form an upper enclosure plate, and the connection between the two plates is made by a four-hole adapter. The lower enclosure plate consists of two identical lower side plates connected to the bottom side plate through a four-hole adapter, forming a side enclosure. The robot is surrounded at the front and rear by four identical oblique anti-collision plates. Four identical bottom center side plates form the bottom enclosure, which is connected to the bottom center plate through a four-hole adapter, forming the bottom enclosure structure.

[0013] Furthermore, the thigh and the two lower legs are connected by plug bolts. Two pairs of flange bearings are embedded in the lower legs. The flange bearings bear radial force, and a thrust bearing is sandwiched between the pair of flange bearings to bear axial force. Two gaskets are used to isolate the inner and outer rings of the flange bearings. Nuts are screwed on to form a rotating pair.

[0014] Furthermore, considering rotational inertia, the length ratio of the pole to the thigh and lower leg is designed to be suitable for jumping, and the topology of the plate is optimized to reduce mass and stress concentration.

[0015] Furthermore, to meet the requirements of the robot climbing slopes, the peak torque T of the hub motor is... max The following relationship must be satisfied between the wheel diameter and the wheel set: Where θ is the ramp angle, m is the mass of the robot, and T max For peak torque, R max Let be the maximum diameter of the wheel assembly, and g be the gravitational constant; the initial velocity v for climbing the slope has the following relationship with the wheel diameter: , where R min Let n be the minimum diameter of the wheel assembly and n be the wheel speed. The overhill power P and the motor torque T have the following relationship: Given θ, m, T maxWhen v, P, n are known, the diameter range of the wheel set can be solved.

[0016] Further, the wheel set comprises two layers of wheel rims and a hub motor, the outer rim is rubberized to form a rubber ring, and is clamped by an inner plate and an outer plate; the inner rim is filled with a support; the inner plate and the outer plate are connected by bolts through the evenly distributed through holes on the wheel rim; the hub motor is connected to the outer plate through a pin coupling and a load reduction plate with a larger diameter than the motor bolt distribution circle, forming a motor rotor; the motor stator is connected to the front calf through a motor connecting piece.

[0017] Further, the guide wheel is clamped between the guide wheel outer mounting plate and the guide wheel inner mounting plate, and the guide wheel is fixed by a spacer column in the middle gap of the guide wheel, and is fixed by mounting bolts and mounting nuts; the guide wheel inner mounting plate is inserted into the guide wheel upper support plate and the guide wheel lower support plate through a plate insertion structure, and the guide wheel outer mounting plate is connected to the guide wheel upper support plate and the guide wheel lower support plate through a four-hole adapter.

[0018] Further, the joint motor connecting piece comprises an inner ring plate with a plurality of first through holes and an outer ring plate with a plurality of second through holes; the joint motor connecting piece is externally connected to a cross roller bearing and a bearing housing; the first through holes are used to connect the motor rotor and the leg, and correspond to the pin holes and bolt holes of the joint motor respectively; the second through holes are used to connect the leg link.

[0019] In this way, the torque generated by the motor and the torque received are borne by the pin, and the bolt only plays a coupling role and is not subject to shear force, so it is not easy to break; the force received by the leg is borne by the bearing, and is not transmitted to the motor, avoiding wear of the threads and ensuring the structural strength.

[0020] In the second aspect, the application also provides a control method of a wheel-leg balance robot capable of active jumping, which adopts the wheel-leg balance robot capable of active jumping described above, and comprises the following processes:

[0021] The robot system model is simplified as an inverted pendulum model, the leg length change of the robot is ignored, and a defined state vector comprises variables related to the posture of the upper mechanism and the leg of the robot and the motion of the driving wheel; the variables include but are not limited to the body posture angle, the swing rod angle, and the angle of the connecting line between the driving wheel shaft and the center of the two joint motor shafts of the leg relative to the inertial system;

[0022] According to the above wheel-leg inverted pendulum model, the control law is designed as a linear combination of the system state, that is:

[0023] wherein, is a state vector, is a control vector; is a feedback gain;

[0024] The feedback gain is calculated by using a linear quadratic regulator (LQR) and the reference input is added to the input of the LQR, i.e.

[0025]

[0026] where the reference input is given by the robot position desired is composed of:

[0027]

[0028] The LQR is linearized and its feedback gain matrix is solved every 10mm in the leg length interval; a polynomial equation is fitted to each element of the matrix to get:

[0029]

[0030] where is the gain matrix related to the leg length, is the value of the matrix K ij when L0=0, i.e. the constant term of the polynomial, is the coefficient of the first derivative of the matrix element with respect to the leg length L0, is the coefficient of the second derivative of the matrix element with respect to the leg length L0, is the coefficient of the third derivative of the element of the feedback gain matrix K ij with respect to the leg length L0, is the leg length;

[0031] It is derived that the longitudinal motion control law of the robot is:

[0032]

[0033] When the robot enters the active jumping mode, the laser ranging module 54 senses the front obstacle and automatically reproduces the jumping control code, and the four joint motors jointly output to perform the control of leg retraction, leg extension and leg retraction, thereby completing the jumping action.

[0034] Further, the inverted pendulum model adopts a segmented modeling manner, first establishes dynamic equations for the driving wheel, the pendulum rod and the body respectively, and then combines these equations by eliminating intermediate variables to obtain a state space model.

[0035] Compared with the prior art, the above-mentioned application has the following advantages or beneficial effects:

[0036] ​​(1) The application takes into account the characteristics of wheeled and legged robots, and designs a wheel-legged balancing robot based on a planar parallel five-bar mechanism; the joint motor connection structure is improved to improve the design strength of the leg structure. By calculating the matching relationship between the wheel diameter and the motor torque of the wheel-legged robot, they are well matched, so that the robot has strong passability.

[0037] (2) The application innovatively uses an inverted pendulum model containing a wheel-leg hybrid structure to fit the robot motion, and adopts an LQR control algorithm to process the feedback gain matrix under different leg lengths through polynomial fitting, segment linearization of the nonlinear system, and addition of reference input to realize trajectory tracking, so that the balancing, obstacle crossing, multi-modal movement, and center of gravity adaptation related motion control methods in the field of biped wheeled robot motion control are improved.

[0038] (3) The application combines multiple sensor modules and innovative control methods to well complete the control of autonomous jumping. BRIEF DESCRIPTION OF DRAWINGS

[0039] The present application and its features, shapes and advantages will become more apparent through reading the detailed description of the non-limiting embodiments with reference to the following drawings. The same reference signs indicate the same parts throughout the drawings. The drawings are not drawn to scale, and the emphasis is on showing the main idea of the present application.

[0040] Figure 1 The overall structure schematic diagram of the wheel-legged balancing robot provided for the embodiments of the present application is shown in the figure.

[0041] Figure 2 The top view structure schematic diagram of the wheel-legged balancing robot provided for the embodiments of the present application is shown in the figure.

[0042] Figure 3 The outside direction structure schematic diagram of one side leg of the robot provided for the embodiments of the present application is shown in the figure.

[0043] Figure 4 The inside direction structure schematic diagram of one side leg of the robot provided for the embodiments of the present application is shown in the figure.

[0044] Figure 5 The connection structure schematic diagram of the connection between the thigh and the shank of the robot provided for the embodiments of the present application is shown in the figure.

[0045] Figure 6 The structure schematic diagram of the thigh of the robot provided for the embodiments of the present application is shown in the figure.

[0046] Figure 7 The structure schematic diagram of the front shank of the robot provided for the embodiments of the present application is shown in the figure.

[0047] Figure 8A structural schematic diagram of a robot rear shank provided by an embodiment of the present application;

[0048] Figure 9 A structural schematic diagram of a robot joint motor connecting piece provided by an embodiment of the present application;

[0049] Figure 10 A cross-sectional structural schematic diagram of a robot joint motor connecting structure provided by an embodiment of the present application;

[0050] Figure 11 A structural schematic diagram of a robot wheel set provided by an embodiment of the present application;

[0051] Figure 12 A central cross-sectional structural schematic diagram of a robot wheel set provided by an embodiment of the present application;

[0052] Figure 13 A schematic diagram of a simplified model of a robot motion system provided by an embodiment of the present application;

[0053] Wherein, 1, wheel set; 2, front shank; 3, rear shank; 4, jam bolt; 5, gasket; 6, thigh; 7, frame; 8, leg limiting block; 9, limiting cushion plate; 10, cushion plate; 11, joint motor; 12, fixed plate; 13, fixed aluminum square; 14, flange shaft; 15, thrust bearing; 16, flange bearing; 17, nut; 18, transverse aluminum square; 19, longitudinal aluminum square; 20, outer plate; 21, load reduction plate; 22, pin coupling; 23, drive wheel motor; 24, motor connecting piece; 25, wheel rim; 26, support; 27, rubber ring; 28, inner plate; 31, transverse baffle; 32, upper support plate of guide wheel; 33, lower support plate of guide wheel; 34, outer installation plate of guide wheel; 35, inner installation plate of guide wheel; 36, guide wheel; 37, cushion column; 38, mounting bolt; 39, mounting nut; 40, reinforcing aluminum square; 41, direct current power supply; 42, power supply support; 43, four-hole adapter; 44, inclined anti-collision plate; 45, center plate; 46, STM32F4 single-chip microcomputer; 47, hardware mounting plate; 48, bottom side plate; 49, bottom center plate; 50, cushion block; 51, anti-collision plate; 52, bottom center side plate; 53, laser ranging module mounting rack; 54, laser ranging module; 55, RFID module; 56, lower side plate; 57, cover plate; 58, positioning module; 59, inner ring annular plate; 591, first through hole; 592, second through hole; 60, outer ring annular plate; 61, crossed roller bearing; 62, bearing housing. DETAILED DESCRIPTION

[0054] The structure of the present application will be further described below in combination with the drawings and specific embodiments, but is not limited to the present application.

[0055] In the description of the present application, it should be noted that the terms "upper", "lower", "front", "back", "left", "right" and the like indicate the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features referred to. Therefore, the features defined with "first", "second" and the like can explicitly or implicitly include one or more of the features.

[0056] In the description of the present application, it should be noted that unless otherwise explicitly specified and limited, the terms "set", "connected" should be understood broadly, for example, it can be fixedly connected, or detachably connected, or integrally connected; the mode can be welding, or threaded connection or binding connection; it can be directly connected, or indirectly connected through an intermediate medium. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances. The standard parts used can be purchased from the market, and can be customized according to the description and drawings. The specific connection mode of each part uses conventional means such as bolts, rivets and welding in the prior art. The mechanical, parts and equipment use conventional models in the prior art, and the components known to those skilled in the art are known to the skilled person through technical manuals or conventional experimental methods.

[0057] In order to make the purpose, technical scheme and advantages of the present application clearer, the embodiments of the present application will be further described in detail below with reference to the drawings.

[0058] Embodiment

[0059] Please refer to Figure 1 and 2 The embodiment provides a wheel-leg balance robot design capable of active jumping, which comprises a chassis, leg link structures on the left and right sides of the chassis, a wheel set 1 at the bottom of the leg link structure, power hardware and control hardware connected with the chassis.

[0060] The leg linkage structure is a planar parallel five-bar linkage, including a frame 7 fixed to the chassis, two thighs 6 located on the outside of the frame 7, and a front lower leg 2 and a rear lower leg 3 rotatably connected to the thighs 6; the wheel hub motor stator of the wheel set 1 is installed at the bottom of the front lower leg 2, and the corresponding position at the bottom of the rear lower leg 3 is connected by a flange shaft 14 to form a rotating pair; in order to provide support when the robot falls after power failure, and to obtain the robot's tilting angle from the joint motor encoder after power is restored, a pair of guide wheels 36 are respectively set on the front and rear sides of the chassis, and a laser ranging module 54 is provided at the bottom front, with a positioning module 58 inside;

[0061] The thigh 6 is connected to the rotor of the joint motor 11 via the frame 7 and the joint motor connector; the stator of the joint motor 11 is fixedly connected to the chassis via the fixing plate 12; the thigh 6 connected to the front lower leg 2 is raised by the shim plate 10 to provide the vertical distance required for the lower leg connection to avoid interference.

[0062] The wheel diameter range is determined based on the initial speed and power requirements for overtaking and the characteristic parameters of the hub motor to achieve a match;

[0063] The control hardware consists of two microcontrollers 46, and two central boards 45 are set up to distribute the power to the circuit.

[0064] More specifically, in this embodiment, see Figures 3 to 5 The leg linkage structure of the wheeled robot is a planar five-degree-of-freedom parallel five-bar linkage. The linkages of the upper arm and lower arm on both sides are centrally symmetrical and have the same length ratio.

[0065] The leg mechanism is connected to a "well"-shaped frame composed of horizontal aluminum squares 18 and vertical aluminum squares 19 via fixed aluminum squares 13, forming the main structure of the chassis. As part of the robot chassis, sheet metal is also used to cover and shield the robot's wiring. The robot chassis is connected to the frame 7 via a horizontal baffle 31 to form an upper enclosure plate, with the two plates connected by a four-hole adapter 43. The lower enclosure plate consists of two identical lower side plates 56 connected to the bottom side plate 48 via four-hole adapters 43, forming a side enclosure. The robot is surrounded at the front and rear by four identical oblique anti-collision plates 44. Four identical bottom center side plates 52 form the bottom enclosure, connected to the bottom center plate 49 via four-hole adapters 43, forming the bottom enclosure structure.

[0066] The planar parallel five-bar linkage consists of a large leg (6), a front lower leg (2), a rear lower leg (3), and a frame. 7The joint motor frame is composed of, from bottom to top, a front lower leg 2 as a mounting plate of a hub motor stator in the wheel set 1, a rear lower leg 3 connected through a flange shaft 14 to form a rotary pair, and two upper legs 6 connected with the two lower legs by means of a set screw 4, which is embedded into the lower leg through setting of two pairs of flange bearings 16, the flange bearings bearing radial force, and a thrust bearing 15 clamped between the two pairs of flange bearings 16 for bearing axial force. Two gaskets 5 are used to isolate the inner and outer rings of the flange bearings 16, and a nut 17 is screwed to form the rotary pair. The connection mode between the front lower leg 2, the rear lower leg 3 and the wheel set 1 is similar to the connection mode of the upper legs, in which a threaded hole is formed on the end face of the flange shaft 14 to screw and position the shaft in the axial direction. The two upper legs 6 are completely identical. Since a certain vertical distance is required for the connection of the lower legs, the left upper leg is raised by a raising plate 10, and in order to ensure that the leg limiting block 8 can limit the left upper leg, a limiting raising plate 9 is arranged in a direction parallel to the left upper leg. In the rotation process of the front lower leg 2, the limiting raising plate 9 rotates synchronously to the leg limiting block 8 to compensate the limiting function, so as to ensure that the leg posture is determined after the robot is powered on again, and the zero position is not lost. A counterbore is formed on the upper end of the upper leg 6 for connecting the counterbore screw to the joint motor connecting piece and connecting with the rotor of the joint motor 11. The stator of the joint motor 11 is connected and fixed with the fixed aluminum square 13 through the fixed plate 12. The fixed aluminum square 13 is fixedly connected with the frame 7. Preferably, the front lower leg 2, the rear lower leg 3, the upper leg 6, the frame 7, the limiting raising plate 9, the raising plate 10 and the fixed plate 12 are all made of carbon fiber material, and the leg limiting block 8 is made of 6061 aluminum alloy material.

[0067] For the structural design of the leg connecting rod, the embodiment also has a relatively detailed design.

[0068] According to the method of determining the proportion, simulation and size, a reasonable rod length proportion suitable for jumping is obtained. According to the formula for calculating the moment of inertia of a rigid body,

[0069]

[0070] In the formula The moment of inertia of the leg connecting rod;

[0071] The mass of the connecting rod;

[0072] The vertical distance from the mass point to the center of rotation.

[0073] It can be seen that the moment of inertia is not only related to the mass, but also related to the mass distribution. At the same time, according to the parallel axis theorem:

[0074]

[0075] In the formula - the moment of inertia of the link mass center around the mass center; - the link mass;

[0076] - the vertical distance of the link mass center from the motor shaft.

[0077] It is thus concluded that the smaller the distance of the link mass center from the motor shaft, the smaller the moment of inertia of the link, and the smaller the torque required by the motor to overcome the link mass. Based on the above analysis, the link structure of the thigh 6 is designed as shown in Figure 6 , the link structures of the shanks 2 and 3 are designed as shown in Figure 7 and 8 , respectively, and the plate material is topologically optimized to reduce the mass and stress concentration.

[0078] Referring to Figure 9 and Figure 10 , the joint motor connecting piece uses an integrated structure developed by Shanghai Jiaotong University, which includes an inner ring annular plate 59 with a plurality of first through holes 591 and an outer ring annular plate 60 with a plurality of second through holes 592; the joint motor connecting piece is externally connected with a cross roller bearing 61 and a bearing housing 62; the first through holes 591 are used to connect the motor rotor and the leg, and correspond to the pin holes and bolt holes of the joint motor, respectively; the second through holes 601 are used to connect the leg link.

[0079] More specifically, the six circular holes in the inner ring of the joint motor connecting piece are used to connect the motor rotor and the leg, and the six holes correspond to the three pin holes and the three bolt holes of the joint motor, respectively, so that the torque generated by the motor and the torque received by the motor are borne by the pins, and the bolts only play a connecting role, so that the bolts are not subjected to shear force and are not easy to break; the six threaded holes in the outer ring of the structure are used to connect the leg link, and the flange edge boss in the outermost ring also plays a positioning role of the inner ring of the cross roller bearing.

[0080] A cross roller bearing 61 is added in the connection between the motor and the leg, so that the force received by the leg is borne by the bearing, and is not transmitted to the motor, avoiding the wear of the threads and ensuring the structural strength. The specific bearing installation is positioned by the inner and outer rings, respectively, the inner ring is acted on by the flange edge of the above-mentioned motor connecting piece, and the outer ring is limited by the bearing housing.

[0081] Referring to Figure 11 and Figure 12In the wheel set 1, the outer ring of the wheel rim 25 is rubberized with polyurethane material with a Shore hardness of 55A, and the rubber ring 27 is formed after rubberization. The material of the wheel rim 25 is 6061 aluminum alloy, which is clamped by the inner plate 28 and the outer plate 20. The inner ring of the wheel rim 25 is filled with the support 26, which facilitates the connection of the inner plate 28 and the outer plate 20 by bolts through the uniform holes on the wheel rim 25. The wheel hub motor 23 is connected to the outer plate 20 through the pin coupling 22 and the load reduction plate 21 with a larger diameter than the bolt distribution circle of the motor, and the motor rotor is connected.

[0082] The design of the wheel train is particularly important in the overall design of the robot, and the size of the driving wheel directly affects the establishment of the robot dynamics model. The selection of the wheel hub motor and the wheel diameter is particularly critical for matching the torque and speed of the robot wheel train. If a wheel hub motor with large torque is selected, its speed will be small, which may not reach the required speed when jumping over obstacles, so it is necessary to increase the radius of the wheel, but increasing the radius of the wheel will increase the torque required to overcome the weight of the robot when climbing uphill, as follows:

[0083]

[0084] θ is the flying slope, m is the mass of the robot, T max is the peak torque, R max is the maximum diameter of the wheel set, and g is the gravitational constant. If the flying slope θ is 17°, T max is the peak torque. It can be seen that if the wheel diameter is increased, the required torque will also increase, and the required torque will decrease if the weight is reduced. At the same time, it is also necessary to satisfy the initial speed of flying slope greater than 2m / s, and leave a certain safety factor, the parameter is designed as 2.5m / s, according to the power:

[0085] Required speed:

[0086] Where T is the torque, R min is the minimum diameter of the wheel set, and n is the wheel speed.

[0087] Combined with the characteristic parameters of the motor, the optimal range of the wheel diameter can be determined to achieve matching.

[0088] As an example, this embodiment considers the effects of too large and too small, and the driving wheel set of the robot has an outer diameter of 220mm.

[0089] Preferably, an RFID module 55 is also installed on the bottom center plate, which can be used to identify the positioning tag during jumping. Of course, for use scenarios without positioning tags, the robot can not contain this module.

[0090] As the hardware part of the robot, its power source is 24V DC power supply 41. To prevent the power supply from being hit by ground uneven objects, a bumper plate 51 is arranged below the battery, which is connected to the guide wheel support lower plate 33 through the cushion block 50, and the battery is installed on the longitudinal aluminum square 19 through the battery support frame 42. The controller of the robot is two STM32F4 single-chip microcomputers 46, and two center plates 45 are arranged to distribute power lines, and the robot hardware module is installed on the hardware mounting plate 47.

[0091] In order to enable the robot to be supported after power failure and falling to the ground, the robot tilt angle that the joint motor encoder can obtain after power-on is set by arranging two pairs of guide wheels 36 in front and back. The guide wheels 36 are clamped between the guide wheel outer mounting plate 34 and the guide wheel inner mounting plate 35, and the guide wheels are fixed by the installation bolt 38 and the installation nut 39 with the spacer column 37 in the middle gap part of the guide wheels. The guide wheel inner mounting plate 35 is inserted into the guide wheel upper support plate 32 and the guide wheel lower support plate 33 through the plate insertion structure, and the guide wheel outer mounting plate is connected with the guide wheel upper support plate 32 and the guide wheel lower support plate 33 through the four-hole adapter 43. In order to improve the structural rigidity of the aluminum square frame, the reinforcing aluminum square 40 is arranged on the guide wheel upper mounting plate. Two pairs of guide wheels are arranged in front and back of the chassis, and the structure is completely the same.

[0092] The control method of the above wheel-leg balance robot includes the following processes:

[0093] The robot system model is simplified as an inverted pendulum model, and the leg length change of the robot is ignored. The defined state vector includes variables related to the posture of the upper mechanism and the leg of the robot and the motion of the driving wheel; the variables include but are not limited to the body posture angle, the swing rod angle, and the angle of the connecting line between the driving wheel shaft and the center of the two joint motor shafts relative to the inertial system;

[0094] According to the above wheel-leg inverted pendulum model, the control law is designed as a linear combination of the system state, that is:

[0095] , wherein, is the state vector, is the control vector; is the feedback gain;

[0096] The feedback gain is calculated by using a linear quadratic regulator (LQR), and a reference input is added to the input of the linear quadratic regulator, that is:

[0097]

[0098] The reference input is composed of the robot position expectation

[0099] ​​

[0100] The linear quadratic regulator is linearized every 10mm in the leg length interval and the feedback gain matrix is solved. A polynomial equation is fitted to each element of the matrix to get the change of the matrix with the leg length:

[0101]

[0102] where, is the gain matrix related to the leg length, is the value of matrix K ij when L0=0, i.e. the constant term of the polynomial, is the coefficient of the first order derivative of the matrix element with respect to the leg length L0, is the coefficient of the second order derivative of the matrix element with respect to the leg length L0, is the coefficient of the third order derivative of the element of feedback gain matrix K ij with respect to the leg length L0, is the leg length;

[0103] The longitudinal motion control law of the robot is derived as:

[0104]

[0105] When the robot enters the active jumping mode, the laser ranging module 54 senses the front obstacle and meets the parameter requirements in the wheel-legged robot jumping control model, the jumping control code is automatically reproduced, the four joint motors 11 jointly output, the control of leg retraction-leg extension-leg retraction is performed, and the jumping action is completed.

[0106] More specifically, referring to Figure 13 Due to the complexity of the planar five-link model in dynamics and kinematics analysis, the robot motion system model is simplified as an inverted pendulum model as shown in the following figure. This model mainly focuses on the attitude of the upper mechanism and the leg of the robot and the motion of the driving wheel, and ignores the change of the leg length of the robot, and only considers the attitude of the leg, i.e. the angle of the connecting line between the driving wheel shaft and the center of the two joint motor shafts relative to the inertial system.

[0107] Table 1 Definition table of variables and parameters in the simplified model of the robot motion system

[0108]

[0109] ​​The traditional inverted pendulum model usually only considers single pendulum or double pendulum structure, while the model of the present scheme is a wheel-leg hybrid structure, which contains a driving wheel, a pendulum rod (the connecting line of the driving wheel shaft and the rotation shaft of the leg mechanism) and a body (upper mechanism), so that the system has more degrees of freedom and the dynamic equation is more complex. See Table 1. Unlike the traditional inverted pendulum, the present embodiment adopts a segmented modeling method to directly establish the overall Lagrange equation:

[0110] The dynamic equation of the driving wheel is constructed as follows:

[0111]

[0112]

[0113]

[0114] The dynamic equation of the pendulum rod is constructed as follows:

[0115]

[0116]

[0117]

[0118] The dynamic equation of the body is constructed as follows:

[0119]

[0120] State space model:

[0121] The state vector is defined as and the control vector is defined as

[0122]

[0123] The system nonlinear model is defined as

[0124]

[0125] Using the MATLAB symbolic operation tool, the intermediate variables in equations (1.4), (1.5), (1.7) and (1.8) are eliminated according to equation (1.3), (1.6) and (1.9), and the function solve is used to solve the system nonlinear model symbolic expression. According to the state vector and the control vector , the Jacobian matrix at the equilibrium point of the nonlinear model is linearized, that is:

[0126]

[0127] ​​where is the solution of the equation

[0128]

[0129]

[0130]

[0131] Due to the complexity of the expression, the symbol is used instead.

[0132] All state variables can be obtained by direct measurement or fusion calculation, so the system output is:

[0133]

[0134] where is a 6-dimensional identity matrix.

[0135] By substituting the model parameters, the state matrix and the control matrix of the state space model are determined, and the controllable matrix is full rank, so the system is controllable. The output matrix of the system is an identity matrix, so the system is obviously observable.

[0136] According to the above wheel-leg inverted pendulum model, the control law is designed as a linear combination of the system state, that is:

[0137]

[0138] The feedback matrix is calculated using the Linear Quadratic Regulator (LQR), and the cost function is defined as:

[0139]

[0140] In order to minimize the cost function , the input should satisfy:

[0141]

[0142] That is, the feedback gain satisfies:

[0143]

[0144] where satisfies the algebraic Riccati equation:

[0145] ​​

[0146] By the above method, the system can be stabilized near the linearization equilibrium point. In order to make the robot track the trajectory, a reference input needs to be added to the system input, that is:

[0147]

[0148] Where the reference input is composed of the robot position expectation :

[0149]

[0150] In order to consider the working conditions of robots with different leg lengths, the system model is linearized every 10 mm within the leg length interval, and the feedback gain matrix is solved, that is, the nonlinear system is processed by piecewise linearization, and the feedback gain matrix K of each linearization point is solved. The polynomial equation of each element of the matrix with respect to the change of leg length is obtained:

[0151]

[0152] The formula derivation shows that the longitudinal motion control law of the robot is:

[0153]

[0154] The above control method makes the controller better adapt to the working state of the wheel-legged robot under different leg lengths, and its implementation can be verified by building a simple simulation model with matlab simscape multibody.

[0155] Substituting the structural parameters of the simulation model, the system model under the leg length :

[0156]

[0157] The LQR weight matrix is selected as:

[0158]

[0159] Solving the Riccati equation can obtain the gain matrix

[0160]

[0161] Let the robot track the step speed expectation :

[0162]

[0163] Integrating it can obtain the expected position of the robot The robot desired state vector is:

[0164]

[0165] Using a field with positioning marks as an example, during the robot's movement, the RFID module 55 senses the tag on the ground, and the robot enters the automatic jumping mode. When the laser ranging module 54 fixed on the laser ranging module mounting frame 53 senses an obstacle in front, the automatic jumping control code is reproduced, the four joint motors 11 jointly output, the leg is controlled to be retracted-extended-retracted, and the jumping action is completed. After the jumping is completed, the RFID module 55 detects the tag indicating that the jumping is completed, and the manual mode is unlocked. After the control mode is switched, the robot can be operated by the remote controller at this time.

[0166] It should be noted that the device structure and the drawings of the present application mainly describe the principles of the present application. In the technical principle of the design, the power mechanism, the power supply system and the control system of the device are not completely described, and the specific power mechanism, the power supply system and the control system can be clearly understood by the skilled in the art on the premise of understanding the principles of the above application. The control mode of the application file is automatically controlled by the controller, and the control circuit of the controller can be realized by programming by the skilled in the art.

[0167] Those skilled in the art should understand that the skilled in the art can realize the variation examples in combination with the prior art and the above embodiments, which are not described here. Such variation examples do not affect the essential content of the present application, and are not described here.

[0168] The above describes the preferred embodiments of the present application. It should be understood that the present application is not limited to the above specific embodiments, and the devices and structures not described in detail should be understood as being implemented in the ordinary way in the art; any skilled in the art can make many possible changes and modifications to the technical solutions of the present application, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solutions of the present application, which does not affect the essential content of the present application. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present application, without departing from the technical solutions of the present application, still belongs to the scope of protection of the technical solutions of the present application.

Claims

1. A wheeled-legged balancing robot structure capable of active jumping, comprising a chassis, leg linkage structures on its left and right sides, a wheel assembly (1) at the bottom of the leg linkage structures, and power hardware and control hardware connected to the chassis; characterized in that: The leg linkage structure is a planar parallel five-bar linkage, including a frame (7) fixed to the chassis, two thighs (6) located on the outside of the frame (7), and a front lower leg (2) and a rear lower leg (3) rotatably connected to the thighs (6); the bottom of the front lower leg (2) is equipped with the stator of the wheel hub motor in the wheel set (1), and the corresponding position of the bottom of the rear lower leg (3) is connected by a flange shaft (14) to form a rotating pair; a pair of guide wheels (36) are respectively provided on the front and rear sides of the chassis, and a laser ranging module (54) is provided at the front bottom of the wheel hub, and a positioning module (58) is provided inside the wheel hub. The thigh (6) is connected to the rotor of the joint motor (11) via the frame (7) and the joint motor connector; the stator of the joint motor (11) is fixedly connected to the chassis via the fixing plate (12); the thigh (6) connected to the front lower leg (2) is raised by the raising plate (10); a leg limiting block (8) is provided at the connection between the thigh (6) and the frame (7), wherein a limiting raising plate (9) is installed at the thigh (6) connected to the front lower leg (2); The wheel diameter range is determined based on the initial speed and power requirements for overtaking and the characteristic parameters of the hub motor to achieve a match; The control hardware consists of two microcontrollers (46) and two central boards (45) are set up to distribute the power to the circuit; To meet the requirements of robot crossing slope, the peak torque T of the wheel hub motor max The following relationship is met between the wheel diameter of the wheel set (1) and the slope θ: , where θ is the crossing slope, m is the mass of the robot, T max is the peak torque, R max is the maximum diameter of the wheel set, and g is the gravitational constant; the following relationship exists between the initial speed v of crossing slope and the wheel diameter: , where R min is the minimum diameter of the wheel set, and n is the wheel speed; the following relationship exists between the crossing slope power P and the motor torque T: ; given θ, m, T max , v, P, and n, the diameter range of the wheel set can be solved.

2. The wheel-legged balanced robot structure capable of active hopping according to claim 1, characterized in that, The main structure of the chassis includes a "well" shaped frame composed of horizontal aluminum squares (18) and vertical aluminum squares (19), and the robot circuit is covered and shielded by plates. Fixed aluminum squares (13) and hardware mounting plates (47) are fixedly connected to the "well" shaped frame. The robot chassis is connected to the frame (7) through a horizontal baffle (31) to form an upper enclosure plate. The connection between the two plates is made by a four-hole adapter (43). The lower enclosure plate is composed of two identical lower side plates (56) connected to the bottom side plate (48) through a four-hole adapter (43) to form a side enclosure. The robot is surrounded by four identical oblique anti-collision plates (44) at the front and rear. The four identical bottom center side plates (52) form the bottom enclosure, which is connected to the bottom center plate (49) through a four-hole adapter (43) to form the bottom enclosure structure.

3. The wheel-legged balanced robot structure capable of active hopping according to claim 1, characterized in that, The thigh (6) is connected to the two lower legs by bolts (4). Two pairs of flange bearings (16) are embedded in the lower legs. The flange bearings bear radial force, and a thrust bearing (15) is sandwiched between the pair of flange bearings (16) to bear axial force. Two gaskets (5) are used to isolate the inner and outer rings of the flange bearings (16), and nuts (17) are screwed on to form a rotating pair.

4. The wheel-legged balanced robot structure capable of active hopping according to claim 1, characterized in that, Considering rotational inertia, the bar length ratio for the thigh and lower leg is designed to be suitable for jumping, and the topology of the plate is optimized.

5. The wheel-legged balanced robot structure capable of active hopping according to claim 1, characterized in that, The wheel group (1) comprises two layers of wheel rims (25) and wheel hub motors (23), the outer rim is coated with rubber to form a rubber rim (27), and is clamped by an inner plate (28) and an outer plate (20); The inner rim is filled with a support member (26); the inner plate (28) and the outer plate (20) are connected by bolts through evenly distributed through holes on the wheel rim (25); the wheel hub motor (23) is connected to the outer plate (20) through a pin coupling (22) and a load reduction plate (21) with a larger diameter than the motor bolt distribution, forming a motor rotor; the motor stator is connected to the front lower leg (2) through a motor connecting piece (24).

6. The wheel-legged balanced robot structure capable of active hopping according to claim 1, characterized in that, The guide wheel (36) is clamped between the guide wheel outer mounting plate (34) and the guide wheel inner mounting plate (35), and the guide wheel intermediate gap part is padded with a pad column (37), and the guide wheel is fixed through mounting bolts (38) and mounting nuts (39); the guide wheel inner mounting plate (35) is inserted into the guide wheel upper support plate (32) and the guide wheel lower support plate (33) through plate insertion structure, and the guide wheel outer mounting plate is connected with the guide wheel upper support plate (32) and the guide wheel lower support plate (33) through the four-hole adapter (43).

7. The wheel-legged balanced robot structure capable of active hopping according to claim 1, characterized in that, The joint motor connecting piece includes an inner ring plate (59) with a plurality of first through holes (591) and an outer ring plate (60) with a plurality of second through holes (592); the joint motor connecting piece is externally connected with a crossed roller bearing (61) and a bearing shell (62); the first through hole (591) is used to connect the motor rotor and the leg, and corresponds to the pin hole and the bolt hole of the joint motor respectively; the second through hole (601) is used to connect the leg link.

8. A control method of an actively jumpable wheel-leg balance robot, characterized by, The actively jumping wheel-leg balancing robot structure of any one of claims 1-7, The process comprises the following steps: The robot system model is simplified as an inverted pendulum model, the leg length change of the robot is ignored, and a defined state vector includes variables related to the posture of the upper mechanism and the leg of the robot and the motion of the driving wheel; the variables include but are not limited to the body posture angle, the swing rod angle, and the angle of the connecting line between the driving wheel shaft and the center of the two joint motors of the leg relative to the inertial system; According to the above wheel-leg inverted pendulum model, the control law is designed as a linear combination of the system state, that is: wherein, is a state vector, is a control vector; is a feedback gain; The feedback gain is calculated by using a linear quadratic regulator (LQR), and a reference input is added to the input of the linear quadratic regulator, that is: wherein the reference input from the robot position expectation consists of: The linear quadratic regulator is linearized every 10 mm in the leg length interval, and the feedback gain matrix is solved; for each element of the matrix, a polynomial equation is fitted according to the change of the leg length, that is: ； wherein is the leg length dependent gain matrix, is the value of the matrix K ij for L0=0, i.e. the constant term of the polynomial, is the coefficient of the first order derivative of the matrix element with respect to the leg length L0, is the coefficient of the second order derivative of the matrix element with respect to the leg length L0, is the coefficient of the third order derivative of the element of the feedback gain matrix K ij with respect to the leg length L0, is the leg length; It is derived that the longitudinal motion control law of the robot is: ； When the robot enters the active jumping mode, the laser ranging module 54 senses the front obstacle, automatically reproduces the jumping control code, and outputs by the four joint motors (11) to control the leg retraction, leg extension and leg retraction, and completes the jumping action.

9. The control method of the actively hopping wheel-legged balancing robot according to claim 8, wherein, The inverted pendulum model adopts a segmented modeling method, first establishes the dynamic equations of the driving wheel, the swing rod and the body respectively, and then combines these equations by eliminating intermediate variables to obtain a state space model.

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