A low-energy consumption hexapod robot based on nonlinear rope geometric constraints and a foot end linearization compensation method thereof

Abstract

The application relates to a low-energy-consumption hexapod robot based on nonlinear rope geometric constraints and a foot end linearization compensation method thereof, and relates to the field of robot design. In order to solve the problem that the robot leg makes circular arc motion with the hip joint as the center, resulting in transverse displacement of the foot end and affecting the motion precision of the robot, the leg mechanism is arranged on both sides of the fuselage in six pairs and is symmetrically arranged left and right, three leg mechanisms on the same side are sequentially arranged from front to back and are arranged as front legs, middle legs and rear legs, each leg mechanism comprises a thigh, a shank and a foot which are sequentially connected, the thigh is rotatably installed on the fuselage through a hip joint shaft, the thigh and the shank are rotatably connected through a knee joint shaft, and the thigh and the shank form an inverted V shape, and the shank is a telescopic leg; the hip joint driving mechanism can drive the thigh to rotate around the Z axis to control the front and back swing of the thigh; the knee joint driving mechanism can transmit power in the process of the front and back swing of the thigh, convert the rotary motion of the thigh into the extension and contraction motion of the shank, and correct the motion track of the foot end.

Description

Technical Field

[0001] This invention relates to the field of robot design technology, and in particular to a low-energy hexapod robot based on nonlinear rope geometric constraints and a method for straightening the legs. Background Technology

[0002] Multi-legged robots have attracted much attention due to their superior locomotion performance in unstructured environments. However, traditional hexapod robots often face a trade-off between structural complexity and locomotion efficiency. Fully free-degree robots, for example, are equipped with three or more motors per leg, resulting in extremely complex control algorithms and low energy efficiency due to the weight of the motors. For robots with simplified configurations, single-degree-of-freedom hip joint drives are often used to reduce the number of motors. This limits the legs to circular movements centered on the hip joint. This "circular trajectory" produces a lateral displacement perpendicular to the direction of travel when the foot contacts the ground. This lateral displacement causes severe lateral friction between the foot and the ground, increasing energy consumption and making the robot prone to slipping on smooth surfaces, making it unable to maintain a straight course and severely impacting its load-bearing capacity and motion accuracy. Summary of the Invention

[0003] In view of this, the present invention provides a low-energy hexapod robot based on nonlinear rope geometric constraints and its foot linearization compensation method. By rotating the thigh and combining it with rope transmission, the lower leg is moved inward and outward, thereby keeping the vertical distance between the foot and the robot body constant. This composite motion compensates for the lateral displacement of the foot caused by the circular motion of the thigh, so that the projected trajectory of the foot on the ground is approximately a straight line parallel to the robot's forward direction, thus solving the problems of large lateral friction and easy slippage caused by the arc-shaped trajectory of the foot.

[0004] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0005] In a first aspect, the present invention provides a low-energy hexapod robot based on nonlinear rope geometric constraints, comprising a body, leg mechanisms, a hip joint drive mechanism, and a knee joint drive mechanism. The leg mechanism has six legs arranged symmetrically on both sides of the body. The three legs on the same side are arranged sequentially from front to back and are designated as a front leg, a middle leg, and a hind leg. Each leg mechanism includes a thigh, a lower leg, and a foot connected in sequence. The thigh is rotatably mounted to the body via a hip joint axis, and the thigh and lower leg are rotatably connected via a knee joint axis, forming an inverted "V" shape. The lower leg is a retractable leg. The hip joint drive mechanism can drive the thigh to rotate around the Z-axis to control the forward and backward swinging of the thigh. The knee joint drive mechanism can transmit power during the forward and backward swinging of the thigh, converting the rotational motion of the thigh into the extension and retraction motion of the lower leg to correct the movement trajectory of the foot.

[0006] Furthermore, there are six knee joint drive mechanisms, each corresponding to one leg mechanism. Each knee joint drive mechanism includes a rope and a return torsion spring, with a threading hole on the thigh. One end of the rope is fixed to the body, and the other end passes through the threading hole on the thigh and is fixed to the calf for calf restraint. The return torsion spring is sleeved on the knee joint axis, and the support legs at both ends of the return torsion spring are connected to the thigh and calf respectively to drive the calf abduction. When the hip joint drive mechanism drives the thigh to swing forward, the rope gradually loosens, and the return torsion spring drives the calf to gradually abduct, in order to compensate for the inward displacement of the foot caused by the circular motion of the thigh. When the hip joint drive mechanism drives the thigh to swing backward, the rope gradually tightens and exerts a pulling force on the calf, causing the calf to gradually retract inward, in order to compensate for the outward displacement of the foot caused by the circular motion of the thigh.

[0007] Furthermore, each knee joint drive mechanism also includes a rope end fixing plate and a guide wheel. The rope end fixing plate is installed on the machine body, and the guide wheel is installed on the thigh. The rope is fixed to the machine body through the rope end fixing plate, and the rope abuts against the guide wheel before passing through the threading hole on the thigh.

[0008] Furthermore, there are two hip joint drive mechanisms arranged on the left and right sides of the body. Each hip joint drive mechanism corresponds to the three leg mechanisms on the same side. Each hip joint drive mechanism includes a first drive unit and a second drive unit. The first drive unit corresponds to the front leg and is used to control the swing of the front leg. The second drive unit corresponds to the middle and rear legs on the same side and is used to control the swing of the middle and rear legs.

[0009] Furthermore, the first drive unit is a first drive motor, which is arranged inside the body, and the motor shaft of the first drive motor is connected to the hip joint shaft of the front leg to drive the thigh to rotate through the hip joint shaft.

[0010] Furthermore, the second drive unit includes a second drive motor, a first bevel gear, a second bevel gear, and a gear shaft. There are two first bevel gears, which are respectively fitted onto the hip joint shafts of the middle leg and the rear leg. There are two second bevel gears, which are fitted onto both ends of the gear shaft. The two second bevel gears are respectively meshed with the two first bevel gears. The second drive motor is installed inside the body. The motor shaft of the second drive motor is connected to the hip joint shaft of the middle leg or the rear leg, and can control the rotation of the hip joint shaft of the middle leg or the rear leg.

[0011] Furthermore, the lower leg includes an upper leg bar, a lower leg bar, and a leg bar drive cylinder. One end of the upper leg bar is connected to the thigh via a knee joint axis, and the leg bar drive cylinder is installed at the other end of the upper leg bar. The lower leg bar is slidably connected to the upper leg bar and can be driven up and down by the leg bar drive cylinder.

[0012] Furthermore, the fuselage includes a front fuselage section, a rear fuselage section, and a pitch motor. The front fuselage section and the rear fuselage section are arranged front to back and are rotatably connected by a pitch joint shaft. The front fuselage section is keyed to the pitch joint shaft. The housing of the pitch motor is fixed to the rear fuselage section, and the motor shaft of the pitch motor is keyed to the pitch joint shaft, and can drive the front fuselage section to perform pitch movement through the pitch joint shaft.

[0013] Secondly, the present invention provides a method for straightening the foot end of a low-energy hexapod robot based on nonlinear rope geometric constraints. Specifically, for the low-energy hexapod robot based on nonlinear rope geometric constraints described in the first aspect, this method adjusts the installation position of the rope end fixing plate (…). , The compensation effect of the control rope constraint makes the foot trajectory approximately linear, that is, to achieve linear compensation of the foot.

[0014] Preset according to the width limitation of the fuselage The value is based on the radius of rotation of the guide wheel on the thigh relative to the center of the hip joint. and work area The support trajectory is determined according to the following general analytical formula. :

[0015] ,

[0016] ,

[0017] ,

[0018] in, , Intermediate variable, constant The elongation provided for the fuselage section rope length, ( , () represents the coordinates of the rope end fixing plate in the XY plane.

[0019] Further, determine The general analytical formula for the support trajectory is obtained through the following steps:

[0020] The target abduction angle of the lower leg is determined by equidistantly balancing the starting and ending points of the support along the Y-axis. The required rope length variation is then determined by calculating this target abduction angle. Finally, the second rope segment is determined based on the principle of rope length conservation. The change is equal to that of the first rope segment The change in;

[0021] Determine based on the relationship between the rope end fixing plate, guide wheel, and lower leg rope node during the movement. The expression, combined The change equals The relationship between the changes was finally determined. The general analytical formula for the support trajectory;

[0022] The lower leg target abduction angle ,in For hip joint rotation, It is the straight-line distance from the knee joint axis to the point of contact with the foot. The radius of rotation of the thigh. Y-axis coordinate of the foot The constant corresponding to "constant".

[0023] The beneficial effects of this invention compared to the prior art are:

[0024] 1. The hexapod robot of this invention adopts a triangular gait walking mode, which allows the hexapod robot to be supported by three leg mechanisms located on different sides simultaneously, while the other three leg mechanisms perform stepping movements synchronously. Through the cyclical alternation of two sets of triangular supports, the robot can move forward stably and continuously.

[0025] 2. The knee joint drive mechanism of this invention uses the rotational movement of the thigh, combined with rope transmission, to drive the lower leg to abduct and retract inward and outward, thereby maintaining a constant vertical distance between the foot and the robot body. This composite motion compensates for the lateral displacement of the foot caused by the circular motion of the thigh, making the projected trajectory of the foot on the ground approximately a straight line parallel to the robot's forward direction. This design not only makes the robot's structure compact and its walking stable, but also solves the problems of high lateral friction and slippage caused by the arc-shaped trajectory of the foot in existing simplified hexapod robots. In addition, the abduction and retraction of the lower leg is achieved entirely by the rotational movement of the thigh, eliminating the need for a knee joint motor, thus reducing the complexity of joint control. Attached Figure Description

[0026] The accompanying drawings, which form part of this invention, are provided to give a further understanding of the invention.

[0027] Figure 1 This is a schematic diagram of the structure of a low-energy hexapod robot based on nonlinear rope geometric constraints according to the present invention.

[0028] Figure 2 This is a top view of a low-energy hexapod robot based on nonlinear rope geometric constraints according to the present invention.

[0029] Figure 3 This is a schematic diagram of the structure of a low-energy hexapod robot based on nonlinear rope geometric constraints according to the present invention (with the outer shell of the robot removed).

[0030] Figure 4This is a schematic diagram (view from below) of a low-energy hexapod robot based on nonlinear rope geometric constraints according to the present invention.

[0031] Figure 5 This is an assembly drawing of the leg mechanism, hip joint drive mechanism, and knee joint drive mechanism on the left side.

[0032] Figure 6 for Figure 5 A magnified view of a portion of point A in the middle.

[0033] Explanation of reference numerals in the attached figures:

[0034] 1. Fuselage; 11. Front fuselage section; 12. Rear fuselage section; 13. Pitch joint axis; 14. Pitch motor; 2. Leg mechanism; 21. Thigh; 211. Horizontal section; 212. Diagonal brace section; 213. Cable hole; 22. Lower leg; 221. Upper leg bar; 222. Lower leg bar; 23. Leg bar drive cylinder; 24. Foot; 25. Hip joint axis; 26. Knee joint axis; 3. Hip joint drive mechanism; 31. First drive motor; 32. Second drive motor; 33. First bevel gear; 34. Second bevel gear; 35. Gear shaft; 36. Support base; 4. Knee joint drive mechanism; 41. Rope end fixing plate; 42. Rope; 43. Guide wheel. Detailed Implementation

[0035] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0036] Example 1:

[0037] See Figure 1This embodiment describes a low-energy hexapod robot based on nonlinear rope geometric constraints, comprising a body 1, leg mechanisms 2, hip joint drive mechanisms 3, and knee joint drive mechanisms 4. The leg mechanisms 2 consist of six legs symmetrically arranged on both sides of the body 1. The three legs on each side are arranged sequentially from front to back. Specifically, the three legs on the left side of the body 1 are designated as the left front leg, left middle leg, and left hind leg, while the three legs on the right side are designated as the right front leg, right middle leg, and right hind leg. Two hip joint drive mechanisms 3 are symmetrically arranged within the body 1. Each hip joint drive mechanism 3 can drive the three legs on the same side to swing back and forth. The front and hind legs on the same side and the middle leg on the opposite side form a coordinating motion unit, i.e., there are two sets of coordinating motion units. The three legs in each set of coordinating motion units stride in the same direction, while the two sets of coordinating motion units stride in opposite directions. Specifically, the left front leg, left rear leg, and right middle leg form one group, and the right front leg, right rear leg, and left middle leg form another group. The left hip joint drive mechanism 3 drives the left front leg and left rear leg to swing forward / backward, and drives the left middle leg to swing backward / forward. The right hip joint drive mechanism 3 drives the right front leg and right rear leg to swing backward / forward, and drives the right middle leg to swing forward / backward, thus achieving three-point support. Figure 1 and Figure 2 There are six knee joint drive mechanisms 4, with one knee joint drive mechanism 4 corresponding to each leg mechanism 2. The knee joint drive mechanism 4 can transmit power during the back-and-forth swing of the thigh 21, converting the rotational motion of the thigh 21 into the extension and retraction motion of the lower leg 22, so as to correct the movement trajectory of the foot and avoid the problem of foot slippage.

[0038] During the robot's forward movement, three leg mechanisms 2 in one set of coordinated motion units are driven forward by the hip joint drive mechanism 3, while the lower legs 22 of these three leg mechanisms 2 are driven outward and lifted by the corresponding knee joint drive mechanism 4. Meanwhile, three leg mechanisms 2 in another set of coordinated motion units are driven backward by the hip joint drive mechanism 3, while the lower legs 22 of these three leg mechanisms 2 support the ground. Under the reaction force of the ground, the robot body 1 moves forward. The two sets of coordinated motion units alternately perform stepping movements in opposite directions, forming a triangular gait walking pattern. This design allows the hexapod robot to always have three leg mechanisms 2 located on different sides simultaneously supporting the body 1, while the other three leg mechanisms 2 perform stepping movements synchronously. Through the cyclical alternation of the two sets of triangular supports, the robot achieves stable and continuous forward movement.

[0039] See Figure 1In this embodiment, each leg mechanism 2 includes a thigh 21, a lower leg 22, and a foot 24 connected in sequence. The thigh 21 adopts a bent rod structure, specifically formed by a horizontal part 211 and a diagonal support part 212 integrally formed; the end of the horizontal part 211 is rotatably mounted to the body 1 via a hip joint axis 25, while the diagonal support part 212 extends obliquely upward. The lower leg 22 mainly consists of an upper leg rod 221, a lower leg rod 222, and a leg rod drive cylinder 23. One end of the upper leg rod 221 is rotatably connected to the extension end of the thigh 21 via a knee joint axis 26, thereby forming the knee joint of the leg; the other end of the upper leg rod 221 extends obliquely downward, and the upper leg rod 221 and the diagonal support part 212 of the thigh 21 form a retractable "V" shape structure, making the overall leg shape resemble a "spider leg". The other end of the upper leg bar 221 is slidably connected to the lower leg bar 222. The leg bar drive cylinder 23 is installed at the other end of the upper leg bar 221, and the drive end of the leg bar drive cylinder 23 is fixedly connected to the lower leg bar 222 for driving the extension and retraction of the lower leg bar 222 relative to the upper leg bar 221. The bottom end of the lower leg bar 222 is fixedly connected to the foot 24.

[0040] See Figure 1 In this embodiment, each knee joint drive mechanism 4 adopts a rope-driven design. The power generated by the swing of the thigh 21 can be transmitted to the lower leg 22 through the rope 42, causing the lower leg 22 to perform extension and retraction movements to adjust the vertical distance between the foot and the body 1, thereby adjusting the movement trajectory of the robot's foot and preventing the robot from slipping. Specifically, the knee joint drive mechanism 4 in this embodiment includes a rope end fixing plate 41, a rope 42, a guide wheel 43, and a return torsion spring (not shown in the figure). The rope end fixing plate 41 is installed on the upper surface of the body 1 and close to the thigh 21. The guide wheel 43 is rotatably installed on the horizontal part 211 of the thigh 21 through a bracket. A threading hole 213 is provided on the thigh 21. One end of the rope 42 is fixed to the rope end fixing plate 41, and the other end passes around the guide wheel 43 and passes through the threading hole 213 of the thigh 21, and then is fixed to the upper leg bar 221 of the lower leg 22. The rope 42 is used to constrain the lower leg 22. The connection point between rope 42 and rope end fixing plate 41 is denoted as point A, the guide point of guide wheel 43 on rope 42 is denoted as point B, and the rope segment between point A and point B is denoted as the first rope segment. The connection point between rope 42 and upper leg 221 is denoted as point C, and the rope segment between point B and point C is denoted as the second rope segment. The reset torsion spring is sleeved at the knee joint axis 26, and the support legs at both ends of the reset torsion spring are connected to the thigh 21 and the lower leg 22 respectively, for driving the lower leg 22 to abduct.

[0041] Figure 1 and Figure 2 The state shown is the initial state of the hexapod robot, which is... Figure 1 and Figure 2It can be seen that the left front leg, left hind leg, and right middle leg of the hexapod robot are at their extreme backward swing positions (the return torsion spring at this extreme position is in an energy-storing state), while the right front leg, right hind leg, and left middle leg are at their extreme forward swing positions. In other words, the left and right leg mechanisms 2 are not symmetrical in the initial state, but are each at their respective extreme positions. In this state, the lower leg 22 of the forward-swinging leg mechanism 2 extends the longest, and the lower leg 22 of the backward-swinging leg mechanism 2 extends the shortest, thus enabling the hexapod robot to maintain a stable ground-supporting state. Since the gait of the left front leg, left hind leg, and right middle leg is consistent, and the gait of the right front leg, right hind leg, and left middle leg is consistent, this embodiment uses the left and right front legs as examples to illustrate the entire movement process of the leg mechanism 2:

[0042] As the hexapod robot moves forward in a straight line, the left hip joint drive mechanism 3 drives the left front leg to rotate counterclockwise around the Z-axis, causing the thigh 21 to swing forward. The guide wheel 43 on the thigh 21 gradually approaches the rope end fixing plate 41. At this time, the rope 42 gradually loosens, and the rope segment between points A and B gradually shortens, i.e., the first rope segment. As the rope gradually shortens, and since the total length of rope 42 remains constant, the usable rope length of the rope segment between points B and C increases accordingly, i.e., the second rope segment. Gradually lengthening, thus making the second rope segment The constraint on the lower leg 22 is relaxed; the return torsion spring releases energy and drives the lower leg 22 to lift and extend outward. The lower leg 22 gradually moves away from the body 1. As the lower leg 22 extends outward, the foot of the left front leg leaves the ground without slipping. When the left front leg reaches its limit position, the leg rod drive cylinder 23 drives the lower leg rod 222 to extend, and the foot of the left front leg supports the ground. At the same time, the right hip joint drive mechanism 3 drives the right front leg to swing backward. The guide wheel 43 on the thigh 21 gradually moves away from the rope end fixing plate 41, and the rope 42 gradually tightens. The rope segment between point A and point B gradually becomes longer, i.e., the first rope segment. As the rope length gradually increases, the usable rope length of the segment between points B and C decreases accordingly, which is the second rope segment. Gradually shortening, thus making the second rope segment A constraint force is applied to the lower leg 22, and the rope 42 overcomes the restoring force of the return torsion spring, pulling the lower leg 22 inward so that it gradually approaches the body 1. Since the foot of the right foreleg is always in contact with the ground, the body 1 is subjected to a reverse force and moves forward, thus realizing the linear forward movement of the hexapod robot. When the right foreleg moves to the extreme position of the backward swing, the leg lever drive cylinder 23 drives the lower leg lever 222 to retract the upper leg lever 221, so that the right foreleg returns to the initial state when it was in the extreme position of the backward swing. After the first gait cycle is completed, the left hip joint drive mechanism 3 starts to drive in the reverse direction, and the right hip joint drive mechanism 3 drives in the forward direction, so that the robot enters the next gait cycle. This cycle repeats, realizing the forward movement of the hexapod robot.

[0043] When the right foreleg swings backward, it rotates counterclockwise around the Z-axis. If the rope 42 does not drive the lower leg 22 to retract inward, the vertical distance between the foot and the body 1 will gradually increase, easily causing the foot to slip. Therefore, this embodiment uses the rotational motion of the thigh 21, transmitted through the rope 42, to convert this into the power to drive the lower leg 22 to retract inward, thus maintaining a constant vertical distance between the foot and the body 1 and effectively preventing slippage. This composite motion compensates for the lateral outward displacement of the foot caused by the circular motion of the thigh 21, making the projected trajectory of the foot on the ground approximately a straight line parallel to the robot's forward direction. This design not only makes the hexapod robot compact and stable in walking, but also solves the problems of high lateral friction and slippage caused by the arc-shaped trajectory of the foot in existing simplified hexapod robots. It should be noted that the inward and outward retraction of the lower leg 22 is entirely achieved by the rotational motion of the thigh 21, eliminating the need for a knee joint motor, thereby reducing the complexity of joint control. Furthermore, the rope 42 used in this embodiment is of fixed length and has no elasticity, which ensures that the rope 42 will not interfere with the movement trajectory of the foot due to length issues.

[0044] See Figure 1 In this embodiment, the hip joint drive mechanism 3 includes a first drive unit and a second drive unit arranged front to back. The first drive unit corresponds to the front leg and is used to control the swing of the front leg; the second drive unit corresponds to the middle and rear legs on the same side and is used to control the swing of the middle and rear legs. Figure 1 In this embodiment, the first drive unit is a first drive motor 31, which is fixed inside the body 1 by a motor mount. The motor shaft of the first drive motor 31 is connected to the hip joint shaft 25 of the front leg to control the rotation of the thigh 21 around the Z-axis. Figure 3 and Figure 4 The second drive unit in this embodiment includes a second drive motor 32, a first bevel gear 33, a second bevel gear 34, a gear shaft 35, and a support base 36. Two first bevel gears 33 are respectively fitted onto the hip joint shafts 25 of the middle and hind legs. The gear shaft 35 is horizontally rotatably mounted within the body 1 via the support base 36. Two second bevel gears 34 are fitted onto both ends of the gear shaft 35, and the two second bevel gears 34 are respectively meshed with the two first bevel gears 33. The second drive motor 32 is fixed within the body 1 via a motor mount. Specifically, the motor shaft of the second drive motor 32 in the left second drive unit is fixedly connected to the hip joint shaft 25 of the left hind leg. The motor shaft of the second drive motor 32 in the right second drive unit is fixedly connected to the hip joint shaft 25 of the right middle leg.

[0045] When the hexapod robot moves forward in a straight line, the two first drive motors 31 on the left and right sides drive their respective thighs 21 to rotate counterclockwise around the Z-axis, causing the left front leg to swing forward and the right front leg to swing backward. The second drive motor 32 on the left side drives the left hind leg to rotate counterclockwise around the Z-axis via the hip joint axis 25 of the left hind leg, causing the left hind leg to swing forward. The first bevel gear 33 on the hip joint axis 25 of the left hind leg rotates counterclockwise accordingly, and through the transmission cooperation of the second bevel gear 34 and the gear shaft 35, drives the first bevel gear 33 on the hip joint axis 25 of the left middle leg to rotate clockwise. This first bevel gear 33 drives the left middle leg to rotate clockwise around the Z-axis via the hip joint axis 25 of the left middle leg, causing the left middle leg to swing backward. Similarly, the second drive motor 32 on the right side drives the right middle leg to rotate counterclockwise through the hip joint shaft 25 of the right middle leg, causing the right middle leg to swing forward. The first bevel gear 33 on the hip joint shaft 25 of the right middle leg rotates counterclockwise, and through the transmission cooperation of the second bevel gear 34 and the gear shaft 35, it drives the first bevel gear 33 on the hip joint shaft 25 of the right hind leg to rotate clockwise. The hip joint shaft 25 of the right hind leg drives the right hind leg to rotate clockwise around the Z-axis, causing the right hind leg to swing backward.

[0046] Obviously, in this embodiment, the movement of the six-legged mechanism 2 can be controlled by the transmission and cooperation of four drive motors and gears, so as to realize the linear motion of the six-legged robot. The reduction in the number of motors reduces the control complexity of the robot, while also enabling the robot to meet the requirements of low energy consumption.

[0047] See Figure 1 In this embodiment, the robot body 1 is configured as two sections, front and rear, allowing the robot to climb slopes by bending these two sections. Specifically, the robot body 1 includes a front body section 11, a rear body section 12, and a pitch motor 14. The front body section 11 and the rear body section 12 are arranged front to back and rotatably connected by a pitch joint axis 13. The front body section 11 is keyed to the pitch joint axis 13. The housing of the pitch motor 14 is fixed to the rear body section 12, and the motor shaft of the pitch motor 14 is connected to the pitch joint axis 13, allowing the front body section 11 to perform pitch movements via the pitch joint axis 13. The left and right front legs are located on the left and right sides of the front body section 11, the left middle leg and left hind leg are located on the left side of the rear body section 12, and the right middle leg and right hind leg are located on the right side of the rear body section 12. A first drive unit is located within the front body section 11, and a second drive unit is located within the rear body section 12.

[0048] When the hexapod robot needs to climb a slope, the pitch motor 14 drives the front body section 11 to tilt upward according to the angle of the slope, so that the left and right front legs can stand upright relative to the slope and support the ground, avoiding the left and right front legs from slipping and causing the robot to fail to climb the slope.

[0049] How a six-legged robot works:

[0050] Straight-line movement: When the hexapod robot moves forward in a straight line, the first drive motor 31 on the left drives the hip joint axis 25 of the left front leg to rotate counterclockwise around the Z-axis, causing the left front leg to swing forward. The second drive motor 32 on the left drives the left hind leg to rotate counterclockwise around the Z-axis via the hip joint axis 25, causing the left hind leg to swing forward; the first bevel gear 33 on the hip joint axis 25 of the left hind leg rotates counterclockwise accordingly, and through the transmission cooperation of the second bevel gear 34 and gear shaft 35, drives the first bevel gear 33 on the hip joint axis 25 of the left middle leg to rotate clockwise. This first bevel gear 33 drives the left middle leg to rotate clockwise around the Z-axis via the hip joint axis 25, causing the left middle leg to swing backward. At the same time, the first drive motor 31 on the right drives the hip joint axis 25 of the right front leg to rotate counterclockwise around the Z-axis, causing the right front leg to swing backward. The second drive motor 32 on the right side drives the right middle leg to rotate counterclockwise through the hip joint shaft 25 of the right middle leg, causing the right middle leg to swing forward. The first bevel gear 33 on the hip joint shaft 25 of the right middle leg rotates counterclockwise, and through the transmission cooperation of the second bevel gear 34 and the gear shaft 35, drives the first bevel gear 33 on the hip joint shaft 25 of the right hind leg to rotate clockwise. The hip joint shaft 25 of the right hind leg drives the right hind leg to rotate clockwise around the Z-axis, causing the right hind leg to swing backward.

[0051] The guide wheel 43 on the thigh 21 of the left front leg, left hind leg, and right middle leg gradually approaches the rope end fixing plate 41. At this time, the rope 42 gradually relaxes, and the section of rope 42 between point A and point B gradually shortens. Since the total length of rope 42 is constant, the available rope length of rope 42 between point B and point C increases accordingly, thereby relaxing the constraint of rope 42 on the lower leg 22. The reset torsion spring releases energy and drives the lower leg 22 to lift up and extend outward. The lower leg 22 gradually moves away from the body 1. As the lower leg 22 extends outward, the foot of the left front leg does not slip off the ground. When the left front leg, left hind leg, and right middle leg move to their limit position, the leg rod drive cylinder 23 drives the lower leg rod 222 to extend, and the feet of the left front leg, left hind leg, and right middle leg support the ground. Meanwhile, the guide wheels 43 on the thighs 21 of the right front leg, right hind leg, and left middle leg gradually move away from the rope end fixing plate 41, the rope 42 gradually tightens, the rope 42 segment between points A and B gradually lengthens, and the available rope length between points B and C shortens accordingly, thus creating a constraint force on the lower leg 22. The rope 42 overcomes the rebound force of the return torsion spring and pulls the lower leg 22 inward, so that the lower leg 22 gradually approaches the body 1. Since the feet of the right front leg, right hind leg, and left middle leg are always in contact with the ground, the body 1 is subjected to a reverse force and moves forward, thereby realizing the linear forward movement of the hexapod robot. When the right front leg, right hind leg, and left middle leg move to the extreme position of the backward swing, the leg rod drive cylinder 23 drives the lower leg rod 222 part to retract the upper leg rod 221, so that the right front leg returns to the initial state when it is in the extreme position of the backward swing. Once the first gait cycle is completed, the left hip joint drive mechanism 3 begins to drive in the reverse direction, while the right hip joint drive mechanism 3 drives in the forward direction, enabling the robot to enter the next gait cycle. This process is repeated to achieve forward movement of the hexapod robot.

[0052] Turning Process: The hexapod robot's turning motion is achieved by controlling the speed difference between the left and right first drive motors 31 and second drive motors 32. Since the left first drive motor 31 and second drive motor 32 control the reciprocating stepping frequency of the three left legs, and the right first drive motor 31 and second drive motor 32 control the reciprocating stepping frequency of the three right legs, when there is a difference in the speed of the left and right drive motors, the stepping speed of the two leg mechanisms 2 will be different, thus causing the hexapod robot to achieve differential turning. When the speed of the left first drive motor 31 and second drive motor 32 is higher than that of the right first drive motor 31 and second drive motor 32, the robot turns right; conversely, it turns left.

[0053] Terrain adaptation control: When the hexapod robot needs to climb a slope, the pitch motor 14 drives the front body section 11 to tilt upward according to the angle of the slope, so that the left and right front legs can stand upright relative to the slope and support the ground, avoiding slipping of the left and right front legs.

[0054] Example 2:

[0055] This embodiment presents a method for straightening the feet of a low-energy hexapod robot based on nonlinear rope geometric constraints. The overall idea for achieving foot straightening is to constrain the "support start position" and "support end position" to make the distance in the Y-axis direction of the foot equal, thereby determining the installation position of the rope end fixing plate 41. In other words, by controlling the installation position of the rope end fixing plate 41... , This is to compensate for the linearization of the foot end.

[0056] In determining the installation position of the rope end fixing plate 41, the distance in the Y-axis direction of the foot end is made equal by constraining the "support starting point position" and the "support ending point position", and the target abduction angle of the lower leg required for the "rotation support process" is calculated; then, the required length of rope change (that is, the constraint length of rope 42, because the second rope segment) is determined by calculating the target abduction angle of the lower leg. The length of the rope constrains the abduction angle of the lower leg target; then, according to the principle of rope length conservation, it is possible to determine... The decrease = The increase in quantity; because the three points of "rope end fixing plate", "guide wheel" and "lower leg rope node" are approximately on the same horizontal reference plane during the movement, therefore =The formula for the distance between the two points, "fixed point" and "thigh guide point", makes The change equals The change in the quantity of change ultimately yields the coordinates of the rope end fixing plate 41. , To clarify the motion mechanism of the hexapod robot in this embodiment and to determine the coordinates of the rope end fixing plate 41 ( , Based on the value rules of ), this embodiment establishes a kinematic vector model of a single-leg system and derives a general analytical formula for realizing the linear support trajectory of the foot.

[0057] S1. Coordinate system definition and mechanism kinematic parameters:

[0058] Establish a spatial rectangular coordinate system: Let the center of rotation of the hip joint be the origin O (0,0,0); the X-axis is the forward direction along the robot body 1, with forward being positive; the Y-axis is the horizontal direction along the body 1, with outward being positive; and the Z-axis is the vertical direction, with upward being positive.

[0059] The key geometric parameters are defined as follows:

[0060] (Hip joint rotation angle): The angle between the horizontal projection axis of thigh 21 and the Y-axis. Defined when thigh 21 is perpendicular to the side of fuselage 1. =0, forward swing is positive. The range of motion of the support phase is defined as follows: .

[0061] (Thigh 21 rotation radius): The projected length of the distance from the hip joint axis to the knee joint axis on the XY plane.

[0062] (22 effective bar lengths for the lower leg): The straight-line distance from the knee joint axis to the point of contact with the foot.

[0063] (Lower leg 22 abduction angle): Lower leg 22 effective link The angle between the angle and the vertical direction (-Z) is defined as positive when it extends outward.

[0064] (Inner angle of the knee joint): The interior angle of the triangle formed by the guide point of the thigh 21, the axis of the knee joint, and the rope node of the lower leg 22. Its angle is different from the abduction angle of the lower leg 22. There exists a fixed linear mapping relationship: ,in This is the inherent installation angle determined by the mechanical structure.

[0065] S2, Target constraint equation for the straight trajectory of the foot:

[0066] To eliminate lateral slippage of the robot's support phase, the trajectory of its feet in the horizontal plane should be a straight line parallel to the X-axis. That is, at any angle of the support phase... Below, the Y-axis coordinate of the foot It should be constant. .

[0067] Establish the kinematic equations for the foot position:

[0068] ,

[0069] make = The abduction angle function of the lower leg 22 target, which is required to maintain a straight trajectory, can be solved inversely. :

[0070] ,

[0071] This indicates that: with the hip joint rotation angle The increase ( (Reduce), lower leg 22 target abduction angle Nonlinear scaling is required to compensate for the circumferential adduction effect of the hip joint.

[0072] S3, Rope-Knee Joint Transmission Model:

[0073] This embodiment utilizes the geometric constraints of a fixed-length rope 42 to drive knee joint movement. The side lengths of the transmission triangle at the knee joint are defined as follows: The distance from guide wheel 43 to the knee joint axis; 22 rope nodes for the lower leg The distance to the center of the knee joint; For the guide wheel 43 to the lower leg 22 rope node The length of the rope between (i.e., the second rope segment) ).

[0074] According to the law of cosines, establish the second rope segment. With the inner angle of the knee joint Relationship:

[0075] ,

[0076] Substitution and by Received The second rope segment required to satisfy the straight trajectory can be obtained. Function of hip joint rotation angle :

[0077] .

[0078] S4, Solution model for the coordinates of the rope end fixing plate 41:

[0079] Assume the total length of rope 42 is a constant value. According to the principle of rope length conservation, the first rope segment Must meet:

[0080] ,

[0081] On the other hand, constructing from geometric spatial location The form of expression:

[0082] set up ( , Let 41 be the coordinate of the rope end fixing plate 41 to be determined in the XY plane; Let be the radius of rotation of guide wheel 43 relative to the center of the hip joint. The coordinates of guide wheel 43 follow... The change is as follows:

[0083] ,

[0084] In this embodiment, the three points—"rope end fixing plate 41," "guide wheel 43," and "lower leg 22 rope node"—are approximately on the same horizontal reference plane during movement. Therefore, the first rope segment... The geometric distance equation is:

[0085] .

[0086] S5, Analytical solution formula for the coordinates of the rope end fixing plate 41:

[0087] In order to determine the coordinates of the rope end fixing plate 41 ( , This embodiment uses the feature point matching method. The endpoint of the support phase is selected ( =0) and the starting point ( = Establish constraint equations.

[0088] S5.1 Define the rope length compensation constant required for a straight trajectory. :

[0089] Based on the goal of "straightening the foot," first calculate the distance at the knee joint (second rope segment). The necessary change in length. Let... To satisfy the ideal abduction angle of the lower leg of 22 required for a straight trajectory.

[0090] Define constants The first rope segment Required elongation:

[0091] ,

[0092] in:

[0093] ,

[0094] .

[0095] S5.2 Establish the constraint equations for the coordinates of the rope end fixing plate 41:

[0096] Based on the geometric relationship of rope length, the first rope segment The change should be equal to :

[0097] ,

[0098] Substituting into the geometric coordinate formula: At that time, the coordinates of the guide point 21 on the thigh were (0, ).exist At that time, the coordinates of the guide point 21 on the thigh were... .

[0099] Get about , The core equation:

[0100] .

[0101] S5.3, Coordinates of rope end fixing plate 41 about The parsing expression:

[0102] Since the above equation contains two unknowns, in engineering design, the width of the fuselage is usually predetermined. Value, and thus solve .

[0103] To simplify the expression, let:

[0104] , , ,

[0105] By rearranging and simplifying the core equation, we obtain the following derivation regarding... The quadratic equation of :

[0106] ,

[0107] The expressions for each coefficient are as follows:

[0108] Quadratic coefficient:

[0109] ,

[0110] coefficient of the first term:

[0111] ,

[0112] The final derivation Analytical solution expression:

[0113] Let the intermediate variable be:

[0114] ,

[0115] ,

[0116] but This can be obtained by solving the following equation:

[0117] ,

[0118] According to the quadratic formula Because the rope end fixing plate 41 must be located in front of the hip joint ( >0), take the positive root:

[0119] .

[0120] Using the above analytical formula, given the robot's mechanical dimensions ( , , , , ) and work area ( After that, the installation position of the rope end fixing plate 41 can be accurately calculated. This not only ensures that the lateral position of the foot at the start and end of the support phase is strictly coincident, but also benefits from the similar nonlinear curvature characteristics of the adduction compensation curve generated by the geometric constraint of rope 42 and the outward displacement curve generated by the hip joint rotation within the working range. This makes the residual error of the trajectory during the entire continuous motion process negligible, thus effectively achieving the foot to move forward approximately along a straight line and greatly reducing the lateral sway of the foot.

[0121] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions created by the present invention, and are not intended to limit the scope of protection of the present invention. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions created by the present invention without departing from the essence and scope of the technical solutions created by the present invention.

Claims

1. A method for straightening the foot ends of a low-energy hexapod robot based on nonlinear rope geometric constraints, characterized in that, Compensation is provided for a low-energy hexapod robot based on nonlinear rope geometric constraints. The robot includes a body, leg mechanisms, a hip joint drive mechanism, and a knee joint drive mechanism. The leg mechanism comprises six legs symmetrically arranged on both sides of the body. The three legs on each side are arranged sequentially from front to back and are designated as the front leg, middle leg, and hind leg. Each leg mechanism includes a thigh, a lower leg, and a foot connected in sequence. The thigh is rotatably mounted to the body via a hip joint axis, and the thigh and lower leg are rotatably connected via a knee joint axis, forming an inverted "V" shape. The lower leg is retractable. The hip joint drive mechanism drives the thigh to rotate around the Z-axis to control its forward and backward swinging motion. The knee joint drive mechanism transmits power during the thigh's forward and backward swinging motion, converting the thigh's rotational motion into the lower leg's extension and retraction motion to correct the foot's trajectory. There are six knee joint drive mechanisms, each corresponding to a leg mechanism; each knee joint drive mechanism includes a rope and a return torsion spring, and a threading hole is provided on the thigh; one end of the rope is fixed to the body, and the other end passes through the threading hole on the thigh and is fixed to the calf for calf restraint. The return torsion spring is sleeved at the knee joint axis, and the support legs at both ends of the return torsion spring are connected to the thigh and the lower leg respectively, which is used to drive the lower leg to abduct. When the hip joint drive mechanism drives the thigh to swing forward, the rope gradually relaxes, and the return torsion spring drives the lower leg to gradually abduct, so as to compensate for the inward movement of the foot caused by the circular motion of the thigh. When the hip joint drive mechanism drives the thigh to swing backward, the rope gradually tightens and generates a pulling force on the lower leg, and the lower leg gradually retracts inward, so as to compensate for the outward movement of the foot caused by the circular motion of the thigh. Each knee joint drive mechanism also includes a rope end fixing plate and a guide wheel. The rope end fixing plate is mounted on the machine body, and the guide wheel is mounted on the thigh. The rope is fixed to the machine body through the rope end fixing plate, and the rope abuts against the guide wheel before passing through the threading hole on the thigh. By adjusting the installation position of the rope end fixing plate ( , The compensation effect of the control rope constraint makes the foot trajectory approximately linear, that is, to achieve linear compensation of the foot. Preset according to the width limitation of the fuselage The value is based on the radius of rotation of the guide wheel on the thigh relative to the center of the hip joint. and work area The support trajectory is determined according to the following general analytical formula. : ， ， ， in, , Intermediate variable, constant The elongation provided for the fuselage section rope length, ( , () represents the coordinates of the rope end fixing plate in the XY plane.

2. The method for leg straightening compensation of a low-energy hexapod robot based on nonlinear rope geometric constraints according to claim 1, characterized in that, Sure The general analytical formula for the support trajectory is obtained through the following steps: The target abduction angle of the lower leg is determined by equidistantly balancing the starting and ending points of the support along the Y-axis. The required rope length variation is then determined by calculating this target abduction angle. Finally, the second rope segment is determined based on the principle of rope length conservation. The change is equal to that of the first rope segment The change in; Determine based on the relationship between the rope end fixing plate, guide wheel, and lower leg rope node during the movement. The expression, combined The change equals The relationship between the changes was finally determined. The general analytical formula for the support trajectory; The lower leg target abduction angle ,in For hip joint rotation, It is the straight-line distance from the knee joint axis to the point of contact with the foot. The radius of rotation of the thigh. Y-axis coordinate of the foot The constant corresponding to "constant".

3. The method for leg straightening compensation of a low-energy hexapod robot based on nonlinear rope geometric constraints according to claim 1, characterized in that, Two hip joint drive mechanisms are provided and arranged on the left and right sides inside the body. Each hip joint drive mechanism corresponds to the three leg mechanisms on the same side. Each hip joint drive mechanism includes a first drive unit and a second drive unit. The first drive unit corresponds to the front leg and is used to control the swing of the front leg. The second drive unit corresponds to the middle and rear legs on the same side and is used to control the swing of the middle and rear legs.

4. The method for leg straightening compensation of a low-energy hexapod robot based on nonlinear rope geometric constraints according to claim 3, characterized in that, The first drive unit is a first drive motor, which is arranged inside the body. The motor shaft of the first drive motor is connected to the hip joint shaft of the front leg so as to drive the thigh to rotate through the hip joint shaft.

5. The method for leg straightening compensation of a low-energy hexapod robot based on nonlinear rope geometric constraints according to claim 4, characterized in that, The second drive unit includes a second drive motor, a first bevel gear, a second bevel gear, and a gear shaft. There are two first bevel gears, which are respectively fitted onto the hip joint shafts of the middle leg and the rear leg. There are two second bevel gears, which are fitted onto both ends of the gear shaft. The two second bevel gears are respectively meshed with the two first bevel gears. The second drive motor is installed inside the body. The motor shaft of the second drive motor is connected to the hip joint shaft of the middle leg or the rear leg, and can control the rotation of the hip joint shaft of the middle leg or the rear leg.

6. The method for leg straightening compensation of a low-energy hexapod robot based on nonlinear rope geometric constraints according to claim 1, characterized in that, The lower leg includes an upper leg bar, a lower leg bar, and a leg bar drive cylinder. One end of the upper leg bar is connected to the thigh via a knee joint axis. The leg bar drive cylinder is installed at the other end of the upper leg bar. The lower leg bar is slidably connected to the upper leg bar and can move up and down driven by the leg bar drive cylinder.

7. The method for leg straightening compensation of a low-energy hexapod robot based on nonlinear rope geometric constraints according to claim 1, characterized in that, The fuselage includes a front fuselage section, a rear fuselage section, and a pitch motor. The front fuselage section and the rear fuselage section are arranged front to back and are rotatably connected by a pitch joint shaft. The front fuselage section is keyed to the pitch joint shaft. The housing of the pitch motor is fixed to the rear fuselage section. The motor shaft of the pitch motor is connected to the pitch joint shaft and can drive the front fuselage section to perform pitch movement through the pitch joint shaft.

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