A wheel-leg composite mobile robot and its control method

Abstract

The present invention discloses a wheel-leg composite mobile robot and its control method. A total of four groups of wheel-leg group mechanisms are provided on both sides of the frame of the robot. The wheel-leg group mechanism includes a leg mechanism, a wheel mechanism, and a gear transmission mechanism; the leg mechanism has two legs; the gear transmission mechanism uses a cam to drive a cam push rod so that the leg mechanism can perform actions such as lifting the leg, stepping the leg, and striding; the wheel mechanism is arranged between the two legs of the leg mechanism and includes a wheel and a cylinder fixed on the frame. The front end of the cylinder is hinged with a long connecting rod, and the other end of the long connecting rod is hinged to the wheel; the end of the cylinder push rod is hinged with a short connecting rod, and the other end of the short connecting rod is hinged to the wheel; a wheel motor is provided on the wheel for driving the wheel to rotate; when the cylinder drives the wheel to retract, the robot is in a leg working mode; when the cylinder drives the wheel to lower, the robot is in a wheel working mode. The present invention can achieve anthropomorphic gait and has better obstacle avoidance ability.

Description

Technical Field

[0001] The present invention relates to a robot, and more particularly to a wheel-leg composite mobile robot and its control method. Background Art

[0002] The deformable wheel-leg composite mobile robot combines the advantages of wheeled mobile robots and legged mobile robots, and has both mobility and obstacle avoidance capabilities.

[0003] The wheel-leg robots proposed in CN107264665A and CN114275071A are provided with radially extensible leg structures on the wheel structure, and the leg structures are driven to rotate by the wheel structure. It can be seen that the wheel-leg robots provided by CN107264665A and CN114275071A are essentially still wheeled robots, which are equivalent to using the extensible leg structures to increase the diameter of the wheel structure, so the obstacle avoidance ability is still relatively limited. Summary of the Invention

[0004] Object of the Invention: The first object of the present invention is to provide a wheel-leg composite mobile robot that can achieve anthropomorphic gait and has better obstacle avoidance ability; the second object of the present invention is to provide a control method for the wheel-leg composite mobile robot.

[0005] Technical Solution: In a first aspect of the present invention, there is provided a wheel-leg composite mobile robot, including a frame, and a total of four groups of wheel-leg group mechanisms are provided on both sides of the frame. The wheel-leg group mechanism includes a leg mechanism, a wheel mechanism, and a gear transmission mechanism;

[0006] The leg mechanism includes two legs and two connecting rods. Support frames are respectively arranged on the outer sides of the two legs. Cam push rods that can slide up and down are arranged on the support frames. The tops of the two cam push rods are connected by a cross bar, and the cross bar passes through the tops of the two legs; one end of the connecting rod is hinged to the support frame, and the other end is hinged to a position above the middle of the outer side of the corresponding leg;

[0007] The gear transmission mechanism uses a cam to drive the cam push rod to enable the leg mechanism to perform actions such as lifting the leg, stepping the leg, and striding;

[0008] The wheel mechanism is arranged between the two legs of the leg mechanism, and includes a wheel and a cylinder fixed on the frame. The front end of the cylinder is hinged with a long connecting rod, and the other end of the long connecting rod is hinged to the wheel; the end of the cylinder push rod is hinged with a short connecting rod, and the other end of the short connecting rod is hinged to the wheel; a wheel motor is arranged on the wheel for driving the wheel to rotate;

[0009] When the cylinder drives the wheel to retract, the robot is in the legged working mode; when the cylinder drives the wheel to lower, the robot is in the wheeled working mode.

[0010] Further, a depth camera is provided at the front end of the frame, and the depth camera is used to collect images in front of the robot.

[0011] Furthermore, foot pads are provided at the bottoms of the two legs.

[0012] Furthermore, a torque sensor is provided on the wheel for collecting the torque when the wheel moves.

[0013] Furthermore, the gear transmission mechanism includes a mounting bracket installed outside the vehicle frame. A second transmission shaft and a third transmission shaft are rotatably installed on the mounting bracket. The third transmission shaft extends into the interior of the vehicle frame, and a first transmission shaft is also rotatably installed on the vehicle frame;

[0014] A first gear is installed on the first transmission shaft, a second gear is installed on the second transmission shaft, a third gear and a fourth gear are installed on the third transmission shaft. The first gear meshes with the fourth gear, and the second gear meshes with the third gear;

[0015] The first transmission shaft and the second transmission shaft respectively pass through two support frames, and two cams are respectively fixed on the first transmission shaft and the second transmission shaft; the first transmission shaft is driven to rotate by a leg motor inside the vehicle frame; the four gears have the same specifications and models, so that the two cams have the same rotational speed and rotation direction.

[0016] Furthermore, the first gear and the fourth gear are located inside the vehicle frame.

[0017] Furthermore, a motor bracket is provided inside the vehicle frame, and the leg motor is fixed on the motor bracket.

[0018] Furthermore, a runner is provided at the lower end of the cam push rod, and the arc surface of the runner contacts the arc surface of the cam below it.

[0019] Furthermore, the wheel-leg composite mobile robot further includes a spring support mechanism. The spring support mechanism includes a spring support frame fixed on the vehicle frame and located in front of the leg mechanism. The spring support frame has a horizontal support column. A spring is sleeved on the horizontal support column and a slider is slidably arranged. The slider can compress the spring when it slides; a crank is hinged on the outside of the support frame close to the vehicle frame, and the other end of the crank is hinged and connected to the slider.

[0020] The second aspect of the present invention provides a control method for a wheel-leg composite mobile robot, including:

[0021] When the robot travels on flat ground, a wheeled working mode is adopted, and differential steering is used for turning;

[0022] When an obstacle appears ahead, an image processing algorithm is used to extract information from the image containing the obstacle collected by the depth camera, calculate the height H of the obstacle, and then compare it with the wheel radius d;

[0023] If the height H of the obstacle is greater than 1 / 2d, it is determined that the robot cannot cross the obstacle; the wheels are retracted upward by using a cylinder, and at the same time the legs touch the ground, and the robot switches to the legged working mode; when all four pairs of legs are on the steps, the wheels are lowered by using a cylinder, and at the same time the legs leave the ground, and the robot switches back to the wheeled working mode;

[0024] If the height H of the obstacle is less than 1 / 2d, it is determined that the robot can cross the obstacle and continue to maintain the wheeled working mode. When the robot travels to the steps, the motor torque is gradually increased. When the torque sensor measures that the motor torque is the set value of the rated torque, if the robot still cannot cross the obstacle, it is determined that the robot cannot cross the obstacle, and then it switches to the legged working mode to cross the obstacle.

[0025] Beneficial effects: Compared with the prior art, the present invention has the following remarkable advantages: (1) The legs are driven by using a cam in cooperation with a cam push rod. When the robot is in the legged working mode, it can achieve anthropomorphic gait and has better obstacle avoidance ability; (2) The legged mode and the wheeled mode can be switched synchronously. When switching between the wheels and the legs, it only needs to control the telescopic movement of the cylinder push rod to achieve, and the control is simple to implement. Brief Description of the Drawings

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required to be used in the embodiments of the present invention. Obviously, the following described drawings are only the embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 is a schematic structural diagram of a wheel-leg composite mobile robot provided by an embodiment of the present application;

[0028] Figure 2 is Figure 1 the bottom view of;

[0029] Figure 3 is a schematic structural diagram of a leg mechanism in an embodiment of the present application;

[0030] Figure 4 is a schematic diagram of the forward extension state of the leg mechanism in an embodiment of the present application;

[0031] Figure 5 is a schematic diagram of the retracted state of the wheels of the wheeled mechanism in an embodiment of the present application;

[0032] Figure 6 is a schematic diagram of the deployed state of the wheels of the wheeled mechanism in an embodiment of the present application;

[0033] Figure 7 is a schematic structural diagram of a gear transmission mechanism in an embodiment of the present application;

[0034] Figure 8 It is a schematic structural diagram of the spring support mechanism in the embodiment of the present application;

[0035] Figure 9 It is a schematic diagram of the leg walking state of the wheel-leg composite mobile robot in the embodiment of the present application;

[0036] Figure 10 It is a schematic diagram of the wheel walking state of the wheel-leg composite mobile robot in the embodiment of the present application;

[0037] Figure 11 It is a flowchart of the control method of the wheel-leg composite mobile robot in the embodiment of the present application;

[0038] Reference numerals: 1, vehicle frame; 2, depth camera; 3, motor bracket; 4, leg motor; 5 / 10, support frame; 6 / 8, connecting rod; 7, cross bar; 9 / 17, cam push rod; 11 / 16, cam; 12 / 15, leg; 13 / 14, foot pad;

[0039] 18, cylinder fixing rod; 19, cylinder; 20, cylinder push rod; 21, short connecting rod; 22, long connecting rod; 23, wheel motor; 24, wheel; 25, torque sensor;

[0040] 26, first transmission shaft; 27, first gear; 28, second transmission shaft; 29, second gear; 30, third gear; 31, mounting bracket; 32, fourth gear; 33, third transmission shaft;

[0041] 34, spring support frame; 35, spring; 36, slider; 37, crank. Detailed implementation manners

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are not all of the embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative efforts belong to the protection scope of the present invention.

[0043] As Figure 1 and Figure 2 shown, it is a schematic structural diagram of a wheel-leg composite mobile robot provided by the embodiment of the present application. The wheel-leg composite mobile robot includes a vehicle frame 1, and a total of four groups of wheel-leg group mechanisms are provided on both sides of the vehicle frame 1. The wheel-leg group mechanism includes a leg mechanism, a wheel mechanism, a gear transmission mechanism, and a spring support mechanism.

[0044] As Figure 3 shown, it is a schematic structural diagram of the leg mechanism. The leg mechanism has two legs arranged parallel and opposite to each other, namely leg 12 and leg 15. A support frame 10 is provided outside leg 12, and a support frame 5 is provided outside leg 15.

[0045] At the top and the upper-middle position of the leg 15, there are reserved holes. The support frame 5 is in an L shape, and a connecting rod 6 is hinged at the end of its short section. The other end of the connecting rod 6 is hinged to the position of the upper-middle reserved hole on the outer side of the leg 15 by screws. A square hole that penetrates up and down is formed on the short section of the support frame 5, and the square hole communicates with the hollowed-out part inside the support frame 5. A cam push rod 17 that is adapted and can slide up and down is arranged in the square hole of the short section of the support frame 5. A runner is arranged at the lower end of the cam push rod 17, and the arc surface of the runner contacts the arc surface of the cam 16 below it.

[0046] The leg 12 and the support frame 10 are connected by a connecting rod 8. A cam push rod 9 that can slide up and down is arranged on the support frame 10. A runner is arranged at the lower end of the cam push rod 9, and the arc surface of the runner contacts the arc surface of the cam 11 below it. The overall leg mechanism is a left-right symmetric structure, so the cooperation relationship among the connecting rod 8, the cam push rod 9, the support frame 10, the cam 11 and the leg 12 will not be elaborated.

[0047] The tops of the cam push rod 9 and the cam push rod 17 are connected by a cross bar 7. At the same time, the cross bar 7 passes through the reserved holes at the tops of the leg 12 and the leg 15, and both the leg 12 and the leg 15 can rotate around the cross bar 7.

[0048] A foot pad 14 is installed at the bottom of the leg 15, and a foot pad 13 is installed at the bottom of the leg 12. The purpose of installing the foot pads is to increase the contact area with the ground, increase the friction, and avoid slipping during the movement. On the other hand, it can prevent the bottom of the leg from directly contacting the ground to achieve the purpose of anti-wear.

[0049] As Figure 7 shown, it is a schematic structural diagram of the gear transmission mechanism. Combining Figure 1 , this gear transmission mechanism includes a mounting bracket 31 installed on the outside of the vehicle frame 1. A second transmission shaft 28 and a third transmission shaft 33 are rotatably installed on the mounting bracket 31. Among them, the third transmission shaft 33 extends into the vehicle frame 1, and a first transmission shaft 26 is also rotatably installed on the vehicle frame 1. A first gear 27 is installed on the first transmission shaft 26, a second gear 29 is installed on the second transmission shaft 28, and a third gear 30 and a fourth gear 32 are installed on the third transmission shaft 33. Among them, the first gear 27 and the fourth gear 32 are located inside the vehicle frame 1, as Figure 2 shown. The first gear 27 meshes with the fourth gear 32, and the second gear 29 meshes with the third gear 30.

[0050] As Figure 2As shown in the figure, a motor bracket 3 is further provided inside the vehicle frame 1, and a leg motor 4 is fixedly installed on the motor bracket 3. The leg motor 4 is used to drive the first transmission shaft 26 to rotate. The first transmission shaft 26 passes through the support frame 5, and the support frame 5 can rotate around the first transmission shaft 26; the cam 16 is fixed on the first transmission shaft 26 and can rotate with the rotation of the first transmission shaft 26. The second transmission shaft 28 passes through the support frame 10, and the support frame 10 can rotate around the second transmission shaft 28; the cam 11 is fixed on the second transmission shaft 28 and can rotate with the rotation of the second transmission shaft 28. The four gears have the same specification and model, and the transmission ratio is 1:1, so that the cam 11 and the cam 16 have the same rotational speed and rotation direction.

[0051] When the two cams rotate synchronously, the corresponding two cam push rods will do reciprocating motions in the vertical direction along their respective support frames, driving the two legs to do up and down motions, imitating the in-place stepping motion of human legs. As Figure 4 shown, when the cam push rod moves to the highest point, the center distance between the two holes of the connecting rod, the distance between the two reserved holes on the leg, and the vertical distance between the two reserved holes just satisfy the Pythagorean theorem, so the leg will expand outward. This process simulates the action of lifting the leg + stepping forward of a person.

[0052] Just realizing the function of lifting the leg + stepping forward, the robot cannot move forward. It also needs to step forward. As Figure 9 shown, it is a schematic diagram of the leg walking state of the wheel-leg composite mobile robot. Since the support frame is sleeved on the transmission shaft, when the cam rotates clockwise, a horizontal component force will be generated on the cam push rod. The cam push rod will squeeze the support frame, causing the support frame to rotate around the corresponding transmission shaft, and then the leg can contact the ground, realizing the functions of lifting the leg + stepping forward + stepping.

[0053] In order to avoid the disturbance caused by the self-weight of the support frame, a spring support mechanism is designed in the embodiment of the present application. Figure 8 The following is a schematic diagram of the structure of the spring support mechanism. Combining Figure 1 , the spring support mechanism includes a spring support frame 34 fixed on the vehicle frame 1 and located in front of the leg mechanism. The spring support frame 34 has a horizontal support column. A spring 35 is sleeved on the horizontal support column and a slider 36 is slidably arranged. The slider 36 can compress the spring 25 when sliding. A crank 37 is hinged on the outside of the support frame 5, and the other end of the crank 37 is hinged to the slider 36.

[0054] The spring 35 has a sufficiently large elastic coefficient. The support frame 5 cannot cause a large deformation of the spring 35 by its own gravity, eliminating the disturbance of the support frame 5 when it is not subjected to a horizontal component force. When the support frame 5 rotates under the action of the cam push rod 17, it will compress the spring 35 and drive the slider 36 to perform a horizontal translation motion. Since the elastic coefficient of the spring 35 is sufficiently large, the rotation amplitude of the support frame 5 is controlled within a certain angular range, avoiding a large rotation angle of the support frame 5 and generating a dead point.

[0055] Combined with Figure 5 , the wheeled mechanism includes a cylinder 19 and a wheel 24. The cylinder 19 is fixed to the outside of the vehicle frame 1 through a cylinder fixing rod 18. A long connecting rod 22 is hinged to the front end of the cylinder 19, and the other end of the long connecting rod 22 is hinged to the wheel 24. The end of the cylinder push rod 20 is hinged to a short connecting rod 21, and the other end of the short connecting rod 21 is hinged to the wheel 24.

[0056] When the cylinder push rod 20 is at the minimum extended length, the short connecting rod 21 is in a horizontal state and the wheel 24 is off the ground. When the cylinder push rod 20 is at the maximum extended length, the short connecting rod 21 is in a vertical state and the wheel 24 is in contact with the ground, as shown in Figure 6 and Figure 10 shown, where Figure 10 is the wheeled walking state of the wheel-leg composite mobile robot.

[0057] The wheeled mechanism passes through from front to back between the two legs of the leg mechanism and does not interfere with each other in the left-right direction. A wheel motor 23 is fixed to the other end of the short connecting rod 21, and the wheel motor 23 is used to drive the wheel 24 to rotate to achieve the wheeled movement of the robot. A torque sensor 25 is installed on the front side of the other end of the long connecting rod 22 and the wheel 24, and the torque sensor 25 is used to collect the torque of the wheel 24 during movement.

[0058] In addition, combined with Figure 1 , a depth camera 2 is provided at the front end of the vehicle frame 1. The depth camera 2 is used to collect the image in front of the robot. When an obstacle appears, the height H of the obstacle is calculated through an image processing algorithm. This image processing algorithm is a prior art and will not be elaborated here.

[0059] The following combines Figure 11 to introduce the control method of the above-mentioned wheel-leg composite mobile robot.

[0060] When the robot is traveling on flat ground, it adopts a wheeled working mode and turns by differential steering.

[0061] When an obstacle appears in front, such as a step, the image processing algorithm is used to extract information from the image containing the obstacle collected by the depth camera 2, calculate the height H of the obstacle, and then compare it with the wheel radius d.

[0062] If the height H of the obstacle is greater than 1 / 2d, it is determined that the robot cannot cross the obstacle; the cylinder 19 is used to retract the wheels 24 upward, and at the same time the legs touch the ground, and the robot switches to the legged working mode. The movement of the four pairs of legs is independent. When crossing an obstacle, a pair of legs on the left front side are first lifted onto the step, and then a pair of legs on the right front side follow closely. The latter two pairs of legs are responsible for providing forward power. When all four pairs of legs are on the step, the cylinder 19 is used to lower the wheels 24, and at the same time the legs leave the ground, and the robot switches back to the wheeled working mode.

[0063] If the height H of the obstacle is less than 1 / 2d, it is determined that the robot can cross the obstacle and continue to maintain the wheeled working mode. When the robot travels to the step, the motor torque is gradually increased. When the torque sensor 25 measures that the motor torque is the set value of the rated torque, for example, 80%, if the robot still cannot cross the obstacle, it is determined that the robot cannot cross the obstacle, and then it switches to the legged working mode to cross the obstacle.

[0064] As described above, it is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any change or replacement solution that can be easily thought of by those skilled in the art within the technical scope disclosed by the present invention should be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. A wheel-leg composite mobile robot, comprising a vehicle frame, and a total of four groups of wheel-leg group mechanisms are arranged on both sides of the vehicle frame, characterized in that, The wheel-leg group mechanism includes a leg mechanism, a wheel mechanism, and a gear transmission mechanism; The leg mechanism includes two legs and two connecting rods. Support frames are respectively arranged on the outer sides of the two legs. Cam push rods that can slide up and down are arranged on the support frames. The tops of the two cam push rods are connected by a cross bar, and the cross bar passes through the tops of the two legs; One end of the connecting rod is hinged to the support frame, and the other end is hinged to a position above the middle of the outer side of the corresponding leg; The gear transmission mechanism uses a cam to drive the cam push rod so that the leg mechanism can perform actions such as lifting the leg, stepping the leg, and striding; The wheel mechanism is arranged between the two legs of the leg mechanism and includes a wheel and a cylinder fixed on the vehicle frame. A long connecting rod is hinged to the front end of the cylinder, and the other end of the long connecting rod is hinged to the wheel; The end of the cylinder push rod is hinged to a short connecting rod, and the other end of the short connecting rod is hinged to the wheel; A wheel motor is arranged on the wheel for driving the wheel to rotate; When the cylinder drives the wheel to retract, the robot is in the leg working mode; when the cylinder drives the wheel to lower, the robot is in the wheel working mode; The gear transmission mechanism includes a mounting bracket installed on the outer side of the vehicle frame. A second transmission shaft and a third transmission shaft are rotatably installed on the mounting bracket. The third transmission shaft extends into the interior of the vehicle frame, and a first transmission shaft is also rotatably installed on the vehicle frame; A first gear is installed on the first transmission shaft, a second gear is installed on the second transmission shaft, a third gear and a fourth gear are installed on the third transmission shaft, the first gear meshes with the fourth gear, and the second gear meshes with the third gear; The first transmission shaft and the second transmission shaft respectively pass through the two support frames, and the two cams are respectively fixed on the first transmission shaft and the second transmission shaft; The first transmission shaft is driven to rotate by a leg motor inside the vehicle frame; The four gears have the same specifications and models so that the two cams have the same rotation speed and rotation direction.

2. The wheel-leg composite mobile robot according to claim 1, wherein A depth camera is arranged at the front end of the vehicle frame, and the depth camera is used to collect images in front of the robot.

3. The wheel-leg composite mobile robot according to claim 1, wherein Foot pads are arranged at the bottoms of the two legs.

4. The wheel-leg composite mobile robot according to claim 1, characterized in that A torque sensor is arranged on the wheel for collecting the torque when the wheel moves.

5. The wheel-leg composite mobile robot according to claim 1, wherein The first gear and the fourth gear are located inside the vehicle frame.

6. The wheel-leg composite mobile robot according to claim 1, characterized in that, A motor bracket is arranged inside the vehicle frame, and the leg motor is fixed on the motor bracket.

7. The wheel-leg composite mobile robot according to claim 1, characterized in that, A runner is arranged at the lower end of the cam push rod, and the arc surface of the runner contacts the arc surface of the cam below it.

8. The wheel-leg composite mobile robot according to any one of claims 1 to 7, characterized in that, It also includes a spring support mechanism. The spring support mechanism includes a spring support frame fixed on the vehicle frame and located in front of the leg mechanism. The spring support frame has a horizontal support column. A spring is sleeved on the horizontal support column and a slider is slidably arranged. The slider can compress the spring when it slides; A crank is hinged to the outer side of the support frame close to the vehicle frame, and the other end of the crank is hinged to the slider.

9. A control method for a wheel-leg composite mobile robot as described in claim 1, characterized in that, Including: When the robot travels on flat ground, it adopts the wheel working mode and uses differential steering for turning; When an obstacle appears ahead, an image processing algorithm is used to extract information from the image containing the obstacle collected by the depth camera, calculate the height H of the obstacle, and then compare it with the wheel radius d; If the obstacle height H is greater than 1 / 2d, it is determined that the robot cannot cross the obstacle; The cylinder is used to retract the wheel upward, and at the same time the legs touch the ground, switching to the leg working mode; When all four pairs of legs are on the step, the cylinder is used to lower the wheel, and at the same time the legs leave the ground, switching back to the wheel working mode; If the height H of the obstacle is less than 1 / 2d, it is determined that the robot can cross the obstacle and continue to maintain the wheeled working mode. When the robot reaches the step, gradually increase the motor torque. When the torque sensor measures that the motor torque is the set value of the rated torque, if the robot still cannot cross the obstacle, it is determined that the robot cannot cross the obstacle, and then switch to the legged working mode to cross the obstacle.

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