CN103707951A - Two-leg robot leg mechanism based on driving of artificial muscles - Google Patents

Abstract

The invention discloses a dual-leg robot leg mechanism driven by artificial muscles, including a single-axis hip joint, a thigh rod, a pneumatic artificial muscle drive mechanism, a bionic knee joint, a calf rod, an ankle joint transmission mechanism and a flexible prosthetic foot; The single-axis hip joint is connected to the thigh rod, the thigh rod is connected to the bionic knee joint, the bionic knee joint, the calf rod, the ankle joint transmission mechanism and the flexible prosthetic foot are connected in sequence, and the pneumatic artificial muscle driving mechanism includes a cross bar, which is vertically fixed on the In the thigh bar, two pneumatic artificial muscles are arranged in parallel, one end is fixedly connected with the cross bar, and the other end is interconnected by a chain, and the chain is connected with the drive shaft of the bionic knee joint through a sprocket, and is pulled by a pair of pneumatic muscles. Implement the drive. It has the characteristics of natural walking gait, strong adaptability to road conditions, small movement impact, fast walking speed, low energy consumption, and can realize flexible joint movement. It also has the advantages of simple structure and delicate design.

Description

Leg Mechanism of Dual-leg Robot Driven by Artificial Muscle

technical field

The invention relates to the field of bionic robots, in particular to a dual-leg robot leg mechanism driven by artificial muscles.

Background technique

The lower limbs of the two-legged robot are connected by a rigid component through a rotating pair, imitating the movement of human legs and hip joints, knee joints and ankle joints, and can replace humans to perform some repetitive labor, or walk in dangerous environments, instead of humans. Work, extend and expand the scope of human activities.

The design of the knee joint is the key to realize the anthropomorphism of the two-legged robot. Drawing lessons from bionics research, simulating the structure of human leg knee joint and muscle drive mode, developing a dual-leg robot leg mechanism based on artificial muscle drive can effectively solve the above-mentioned problems of dual-leg walking robots. Usually, in the research of ordinary two-legged robots, DC servo motors are used as the driving source to provide driving force, and some are driven by hydraulic pressure or air pressure. Although the hydraulic drive is stable and the position accuracy can be very high, its rigidity is often very large, and the hydraulic cylinder is heavy, which requires high sealing performance, and there are cases of leakage and pollution. Pneumatic drive is currently mainly used for point-to-point joint position control with 1/2 degree of freedom, and it has high requirements for the sealing of the cylinder. In addition, some new drivers such as shape memory alloys and magnetostrictive drivers are still in the research and development stage, and there is still a certain distance from practical application. At present, in the research of ordinary two-legged robots, DC servo motors are mostly used to provide drives, and a relative angle encoder is installed behind the motor shaft to measure the rotation angle. The motor drive can realize various gaits and is easy to achieve precise control. When the foot hits the ground, it will generate a large impact force, which will easily cause the rigidity of the motor drive to be too large, and it is difficult to realize the smooth movement of human joints.

After natural selection and long-term evolution, human leg bones are most suitable for walking upright with two legs, and the structural changes of each joint during the selection and evolution process are more conducive to this walking style. At present, the knee joints of two-legged walking robots mostly use single-axis hinges, which are fundamentally different from those of human leg joints in terms of structure, motion mechanism and driving mode, resulting in the inability to simulate human gait well.

1) Differences in the types of joint mechanisms

During the flexion and extension process of the human knee joint, the joint is driven by the stretching movement of the inner and outer muscles, which can rotate and slide, so that the length of the thigh and thigh can be changed, and it has a better obstacle-crossing function. Biomedical studies have shown that the position of the horizontal axis of rotation of the knee joint changes during flexion and extension, and is accompanied by movement during rotation, and the trajectory of its Instant Center of Rotation (ICR) changes according to a "J"-shaped curve. At the same time, changes in the CR of the knee joint and the length of the thigh and thigh can adjust the moment of the ground reaction force acting on the joint and reduce the hip extension muscle force required to stabilize the knee joint, thereby improving the stability of the legs when walking and efficiency.

Compared with human joints, the knee joint structure adopted by walking robots is essentially different. In the design of most active dual-legged walking robots, the knee joint is mostly articulated with two linkages. The ICR is fixed, and the walking gait is unnatural, which is quite different from the normal walking gait of the human body. In order to maintain the stability of the support phase, the robot keeps its legs bent when standing, and the walking speed is slow, which leads to the poor anthropomorphic walking gait of the robot.

2) Differences in joint drive

When a normal human body walks on two legs, the muscles on both sides of the joint receive signals transmitted by the nerves, and the joints are driven to rotate through the telescopic movement of the muscles connected to the ligaments on both sides of the joint. The whole driving process is stable, and the muscles and ligaments with better flexibility can cushion the ground impact of the collision.

At present, in the research of most of the two-legged walking robots, the basic structure is mostly connected by rigid rods. The knee joint is driven by a motor, which is too rigid and has poor flexibility, especially when walking on uneven road conditions, resulting in unstable walking. , which is quite different from the driving mode of human knee joint muscles.

Normal human joints are driven by skeletal muscles, which can not only provide driving force to achieve precise position control, but also can absorb vibration, cushion, and have good flexibility. This characteristic is mainly determined by the antagonistic muscle drive mode adopted by the joints. As a new type of rubber actuator, pneumatic artificial muscle has the characteristics of light weight, simple structure, large output force, good flexibility, and force-length characteristics very similar to human muscles. These are not fully available in other traditional driving methods, so pneumatic artificial muscles are a very suitable choice for driving bionic mobile robots. Many experts and scholars at home and abroad, such as Tao Guoliang, have studied the motion control of humanoid leg joints driven by pneumatic artificial muscles, and have obtained some results.

Although all countries have carried out more in-depth research on the two-legged walking robot at present, they have realized basic human motions such as stable walking of the two legs, going up and down stairs and turning. However, through the analysis of its development process, it can be seen that there are still many problems in the two-legged walking robot:

(1) The walking gait is unnatural, which is quite different from the normal human gait, and the ability to adapt to the ground road conditions is not strong;

(2) Limited by its own mechanical structure, shocks are generated during the movement, and the walking speed is slow;

(3) Most of the joints adopt the active driving mode of the motor, which consumes a lot of energy, and the driving mode is rigid, which is not conducive to realizing the flexible movement of the joints.

Contents of the invention

In order to solve the problems existing in the above-mentioned prior art, the present invention proposes a dual-leg robot leg mechanism driven by artificial muscles, which has natural walking gait, strong adaptability to road conditions, small motion impact, fast walking speed, and low energy consumption , can realize the characteristics of joint flexible movement. It also has the advantages of simple structure and delicate design.

To achieve the above object, the technical solution of the present invention is:

A dual-leg robot leg mechanism driven by artificial muscles, including a single-axis hip joint, a thigh rod, a pneumatic artificial muscle drive mechanism, a bionic knee joint, a calf rod, an ankle joint transmission mechanism and a flexible prosthetic foot; the single-axis hip joint and The thigh shaft is connected, the thigh rod is connected to the bionic knee joint, the bionic knee joint, the calf rod, the ankle joint transmission mechanism and the flexible prosthetic foot are connected in turn, the pneumatic artificial muscle drive mechanism includes a cross bar, which is vertically fixed in the thigh rod, two The pneumatic artificial muscles are arranged in parallel, one end is fixedly connected to the cross bar, and the other end is interconnected by a chain, and the chain is connected to the drive shaft of the bionic knee joint through a sprocket, and the driving is realized by pulling a pair of pneumatic muscles.

The bionic knee joint is a bilateral four-bar mechanism. The four-bar mechanism includes a first axis, a second axis, a third axis, and a fourth axis that are sequentially movably connected through connecting rods. The three axes, the fourth axis, and the first connecting rod, the second connecting rod, the third connecting rod, and the fourth connecting rod connecting them form a trapezium with variable angles, and the first connecting rod of the two four-bar mechanisms The rods form an integral link, and the third links of the two four-bar linkages form an integral link. The thigh rod is fixedly connected with the integral connecting rod composed of two first connecting rods of the four-bar mechanism, and the calf rod is fixedly connected with the integral connecting rod composed of the third connecting rod of the two four-bar mechanism. The calf rod can be wound around the bionic knee during walking. The joint rotates relative to the thigh bar.

The detailed parameters of the bionic knee joint are: the length ratio of the first link, the second link, the third link, and the fourth link is: 17.728:62.749:35.476:49.75, and the third link when standing normally The angle between the rod and the horizontal plane is: 44.92 degrees.

The fourth shaft is a drive shaft.

A snap ring for fixing a sprocket is installed on the drive shaft, and the sprocket is keyed to the drive shaft.

Compared with the prior art, the beneficial effects of the present invention are: the present invention proposes a dual-leg robot leg mechanism driven by artificial muscles, which has

1. Natural walking gait: The ICR of the knee joint is not fixed, but changes with the angle of the knee joint, which can effectively simulate the movement of the normal human knee joint.

2. Strong adaptability to road conditions: In the swing phase, the length of the thigh and thigh rods of the artificial leg can be effectively shortened, thereby increasing the height of the foot lifting and avoiding collision with ground obstacles.

3. Small movement impact: It can effectively use the surface reaction force to maintain the stability of the support phase, and help the machine legs to bend when they leave the ground.

4. Fast walking speed and low energy consumption: driven by pneumatic artificial muscles.

5. Can realize joint flexible movement: In the middle stage of swing or when sitting down, the knee joint will instantly drop to the normal position, which can effectively improve the sitting posture and keep the posture of the knees consistent when sitting down. It also has the advantages of simple structure and delicate design.

Description of drawings

Fig. 1 is a schematic structural diagram of an embodiment of the present invention.

Among them: 1-single-axis hip joint, 2-thigh rod, 3-pneumatic artificial muscle drive mechanism, 31-crossbar, 32-pneumatic artificial muscle, 33-chain, 4-bionic knee joint, 41-first axis, 42 - second shaft, 43- third shaft, 44- fourth shaft, 45- first connecting rod, 46- second connecting rod, 47- third connecting rod, 48- fourth connecting rod, 49- snap ring, 410-sprocket wheel, 5-calf rod, 6-ankle joint transmission mechanism, 7-flexible prosthetic foot.

Fig. 2 is a schematic diagram of the relationship between the length and angle of the four-bar mechanism of the bionic knee joint according to the embodiment of the present invention.

Fig. 3 is a schematic diagram of the structure of the bionic knee joint according to the embodiment of the present invention.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific embodiments.

As shown in Figure 1, the leg mechanism of a dual-leg robot driven by artificial muscles includes a single-axis hip joint, a thigh rod, a pneumatic artificial muscle drive mechanism, a bionic knee joint, a calf rod, an ankle joint transmission mechanism and a flexible prosthetic foot; The single-axis hip joint is connected to the thigh rod, the thigh rod is connected to the bionic knee joint, the bionic knee joint, the calf rod, the ankle joint transmission mechanism and the flexible prosthetic foot are connected in sequence, and the pneumatic artificial muscle drive mechanism includes a cross bar, which is vertically fixed on the In the thigh bar, two pneumatic artificial muscles are arranged in parallel, one end is fixedly connected with the cross bar, and the other end is interconnected by a chain, the chain is connected with the drive shaft of the bionic knee joint through a sprocket, and is pulled by a pair of pneumatic muscles. Implement the drive.

The bionic knee joint is a bilateral four-bar mechanism. The four-bar mechanism includes a first axis, a second axis, a third axis, and a fourth axis that are sequentially movably connected through connecting rods. The three axes, the fourth axis, and the first connecting rod, the second connecting rod, the third connecting rod, and the fourth connecting rod connecting them form a trapezium with variable angles, and the first connecting rod of the two four-bar mechanisms The rods form an integral link, and the third links of the two four-bar linkages form an integral link. The thigh rod is fixedly connected with the integral connecting rod composed of two first connecting rods of the four-bar mechanism, and the calf rod is fixedly connected with the integral connecting rod composed of the third connecting rod of the two four-bar mechanism. The calf rod can be wound around the bionic knee during walking. The joint rotates relative to the thigh bar.

The detailed parameters of the bionic knee joint are: the length ratio of the first link, the second link, the third link, and the fourth link is: 17.728:62.749:35.476:49.75, and the third link when standing normally The angle between the rod and the horizontal plane is: 44.92 degrees.

The fourth shaft is a drive shaft.

A snap ring for fixing a sprocket is installed on the drive shaft, and the sprocket is keyed to the drive shaft.

According to medical research, the human knee joint is composed of the medial and lateral condyles of the femur, the medial and lateral condyles of the tibia, and the patella. Due to the irregular shape of the bone contact surface, there is rolling and sliding between the contact surfaces during joint flexion and extension activities. The curvature center of the horizontal axis of the knee joint, that is, the instantaneous center of rotation, changes from time to time, and its moving track is a "J"-shaped curve. The present invention uses The four-bar mechanism with better bionic properties is used as the robot knee joint structure, as shown in Figure 2. The CR of the four-bar structure changes all the time, and the length of the rods and the angle between the rods can be optimized according to the CR trajectory of the human knee joint, which can better simulate the walking gait of human legs. In terms of mechanism, it fundamentally improves the shortcomings of poor bionicity of the traditional knee joint structure. Compared with the single-axis knee joint, the four-bar knee joint has many advantages: (1) The CR of the knee joint is not fixed, but changes with the angle of the knee joint, which can effectively simulate the movement of the normal human knee joint. , (2) In the swing phase, it can effectively shorten the length of the artificial leg's large and small leg rods, thereby increasing the height of the foot and avoiding collision with ground obstacles, which is consistent with the performance of the normal knee joint during walking; (3) In the mid-swing phase Or when sitting down, the instantaneous center of the knee joint drops to the normal position, which can effectively improve the sitting posture and keep the posture of the knees consistent when sitting down; (4) It can effectively use the surface reaction force to maintain the stability of the support phase and help the machine Bend the leg as it leaves the ground. In order to ensure that the robot leg can maintain balance in the support phase, a limit stop is added to the design of the knee joint to limit the excessive extension of the lower leg. The joints are supported by bearings, and the shafts and hubs are used to connect the rods, and the corresponding cooperation is adopted. At the same time, in order to ensure the stability during walking, a double-sided four-bar mechanism is adopted.

The higher the similarity between the instantaneous heart trajectory of the knee joint mechanism and the human knee joint, the better the coordination between the mechanism and the human body. From this point of view, the objective function is established based on the square of the coordinate difference between the instant center point of the mechanism and the ideal instant center point of the human body, and an optimal design is carried out based on the genetic algorithm. The knee joint parameters of the four-bar mechanism are shown in Figure 2.

The knee joint adopts a four-bar mechanism with four revolving pairs. In theory, each revolving pair can be used as a drive shaft, that is, each connecting shaft can be used as a drive shaft in theory. In practical applications, considering energy saving and specific Mechanical structure, the selection of its drive shaft is limited. Through the analysis of the control torque of the knee joint of the four-bar mechanism, it can be seen that when the calf is turned normally, the torque required for axis 1 is the smallest, followed by axis 4. Therefore, from the perspective of energy saving, the drive shaft should be selected on axis 1 or axis 4. Considering the limitations of the structure of the four-bar mechanism itself, the space at shaft 1 is small, and it is not easy to install transmission systems such as sprockets. Therefore, placing the drive shaft on shaft 4 will not only meet the requirements of the actual mechanical structure, but also reduce energy consumption. .

The present invention selects the pneumatic artificial muscle as the driving source to provide the driving force for the knee joint. A single pneumatic artificial muscle can only provide one-way contraction force. In order to obtain two-way force and rotational movement, a pair of pneumatic artificial muscles is used to pull. The four-bar mechanism is driven by a pair of artificial muscles to drive the sprocket. The sprocket is installed on the drive shaft. It has high transmission precision, simple structure, strong bearing capacity, easy maintenance and long service life. The connection between the sprocket and the drive shaft is connected by a key. In order to prevent the sprocket from sliding axially, it is fixed with a snap ring, as shown in Figure 3.

The invention is based on a robot leg mechanism with two legs driven by artificial muscles. Its working principle is: the hip joint is driven by a motor, the knee joint is driven by a pair of artificial muscles through chain transmission, and the ankle joint is driven by a motor through gear transmission. According to the three-center theorem, the intersection point of the extension line of the second link and the fourth link is the instantaneous center of rotation of the knee joint. Since the positions of the second link and the fourth link are dynamically changing during the movement of the four-bar knee joint Therefore, the intersection of its extension lines, that is, the instantaneous center of rotation, is dynamically variable and approximates a "J"-shaped curve, so that the flexion and extension of the knee joint can be realized, and the coordinated movement of the transmission mechanism of the hip joint, knee joint and ankle joint can be realized. Forward motion of the robot.

Claims (5)

1. the both legs leg mechanism of robot driving based on artificial-muscle, comprises single shaft hip joint, thigh bar, Pneumatic artificial muscle driver train, bionic knee joint, shank bar, ankle-joint transmission device and flexible false pin; It is characterized in that, described single shaft hip joint and thigh bar axle connect, thigh bar connects bionic knee joint, and bionic knee joint, shank bar, ankle-joint transmission device and flexible false pin connect successively, and Pneumatic artificial muscle driver train comprises cross bar, cross bar is vertically fixed in thigh bar, two Pneumatic artificial muscles be arranged in parallel, and one end and cross bar are connected, and the other end interconnects by chain, described chain is connected with the axle drive shaft of bionic knee joint by sprocket wheel, by a pair of pneumatic muscles to drawing to realize driving.

2. the both legs leg mechanism of robot driving based on artificial-muscle as claimed in claim 1, it is characterized in that, described bionic knee joint is bilateral four-bar mechanism, four-bar mechanism comprises the first axle being flexibly connected successively by connecting rod, the second axle, the 3rd axle, the 4th axle, described the first axle, the second axle, the 3rd axle, the 4th axle, and connect their first connecting rod, second connecting rod, third connecting rod, the 4th connecting rod, form the trapezoid of a variable-angle, the first connecting rod of two four-bar mechanisms forms a monolithic linkage, the third connecting rod of two four-bar mechanisms forms a monolithic linkage, thigh bar is connected with the monolithic linkage consisting of two four-bar mechanism first connecting rods, shank bar is connected with the monolithic linkage consisting of two four-bar mechanism third connecting rods, in walking, shank bar can rotate with respect to thigh bar around bionic knee joint.

3. the both legs leg mechanism of robot driving based on artificial-muscle as claimed in claim 2, it is characterized in that, the detail parameters of described bionic knee joint is: the length ratio of described first connecting rod, second connecting rod, third connecting rod, the 4th connecting rod is: 17.728: 62.749: 35.476: 49.75, and during normal stand, the angle of third connecting rod and horizontal surface is: 44.92 degree.

4. the both legs leg mechanism of robot driving based on artificial-muscle as claimed in claim 2, is characterized in that, described the 4th axle is axle drive shaft.

5. the both legs leg mechanism of robot driving based on artificial-muscle as claimed in claim 4, is characterized in that, the snap ring for fixed chain wheels is installed on described axle drive shaft, and described sprocket wheel is connected with driving axle key.

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