Background
"human-machine co-fusion" is the goal of humanoid robot development, directing the direction of research in this field. Although the shape and the function of the existing humanoid robot are more and more humanoid, all have the obvious defect of rigid action. The bionic level of the waist joint of the existing humanoid robot is seriously lagged behind that of other bionic joints, and the wooden barrel effect is obvious.
In the field of joint bionics, as ankle joints, hip joints, elbow joints, wrist joints and finger joints of a human body all belong to spherical joints, the same motion characteristics can be easily realized in mechanics, and the research is relatively mature. However, unlike other human body movement joints, the waist joint is not a spherical joint around a certain rotation center, but a segment composed of multiple joints having a linkage movement property and a superposition of multiple stages of movements, and the degree of movement is highest among the human body joints. In addition, the waist of the human body not only has the function of connecting the upper limb and the lower limb, but also can adjust the gravity center when the human is engaged in various exercises and participate in the control of balance, so the waist has obvious effect on the human body exercises. Once the waist joint of the robot is similar to the waist of a human body, the robot not only has stable gait, but also can complete flexible movement and flexible posture. Li Yanjie has studied in the human-like robot human hair exhibition and the function of the waist joint thereof and Wuweiguo has studied in the human-like robot waist joint balance function research and simulation, which proves the important significance of the bionic waist joint.
However, there is currently no mechanism for achieving this motion characteristic in the true sense. Although the tandem mechanism can realize the motion characteristic by overlapping a plurality of rotating pairs, a corresponding driving unit must be matched for each degree of rotational freedom, and the tandem mechanism has little practical value in terms of overall weight and power and energy efficiency. For the traditional parallel mechanism, a mechanism which can be matched with the working space is hardly found. Therefore, the conventional method must be broken through, the advantages of the two methods are utilized and complemented, a mechanism which has the advantages of rotation, superposition, super-large working space and the number of driving units as few as possible is designed, and the high bionic of the waist of the human body is realized.
Disclosure of Invention
The invention aims to solve the problem that the bionic level of the waist joint of the existing humanoid robot is seriously low in the known technology, and provides the waist joint of the humanoid robot based on the 3-RRR spherical parallel mechanism, which can realize multiple superposition, working space amplification, flexible movement and almost complete coincidence with the movement characteristics of multi-section linkage of the lumbar of a human body.
The parallel mechanism unit is formed by symmetrically coupling odd number of parallel mechanism units with the same structure, is a parallel mechanism with three rotational degrees of freedom, and comprises a fixed platform, a shared platform I or a shared platform II, a tail end platform and three RRR serial branched chains which are connected with every two platforms, have the same structure and are uniformly distributed along the circumferential direction, wherein each RRR serial branched chain comprises a driving rod, a driven rod and a straight bevel gear; one end of a driving rod of each adjacent parallel mechanism unit is fixedly connected with the other straight bevel gear and is connected with the common platform through a revolute pair, the two straight bevel gears are meshed, the other end of the driving rod is connected with one end of a driven rod through the revolute pair, and the other end of the driven rod is fixedly connected with the straight bevel gear and is connected with the other common platform through the revolute pair; arranging a plurality of adjacent parallel mechanism units according to requirements; one end of a driving rod of the tail end of one parallel mechanism unit is connected with the other straight bevel gear and is connected with the shared platform through a revolute pair, the other end of the driving rod is connected with one end of a driven rod through a revolute pair, and the other end of the driven rod is connected with the tail end platform through a revolute pair; the same parallel mechanism unit contains 9 revolute pairs in total, and the axes of the revolute pairs intersect at one point; the two adjacent parallel mechanism units are divided into a front-stage mechanism unit and a rear-stage mechanism unit according to the motion output direction; the symmetrical coupling means that, on the one hand, all components of the preceding mechanism unit and all components of the subsequent mechanism unit are symmetrical with respect to the common platform at any instant, and, on the other hand, the transmission of motion between the parallel mechanism units is realized by additionally arranging a single degree-of-freedom transmission mechanism between the driven rod of the preceding mechanism unit and the driving rod of the subsequent mechanism unit, and the single degree-of-freedom transmission mechanism can equivalently convert the angular change of the driven rod of the preceding mechanism unit into the angular change of the driving rod of the subsequent mechanism unit.
Compared with the prior art, the invention has the following advantages:
(1) the parallel mechanism units based on the 3-RRR parallel mechanism form a human-like waist shape in a symmetrical coupling mode;
(2) the motion characteristics of the symmetrical coupling of the odd number of parallel mechanism units are matched with the motion characteristics of the multi-section linkage of the lumbar vertebra of the human body;
(3) the number of parallel mechanism units participating in coupling does not influence the number of required driving units, and only three groups of driving units are needed;
(4) two adjacent parallel mechanism units are symmetrical about the shared platform, and all the parallel mechanism units can deflect towards the same direction at any moment;
(5) the total deflection angle is equal to the sum of the deflection angles of all the parallel mechanism units in a symmetrical coupling mode, the effects of multiple superposition and working space amplification are realized, and the movement is flexible;
(6) the rotation of the movable platform relative to the fixed platform and the rotation of the movable platform relative to the fixed platform of the input end parallel mechanism unit have a determined multiple relation, so that the position analysis can be converted into the position analysis of the parallel mechanism unit, the calculation model is simplified conveniently, and the practical application is facilitated.
Drawings
FIG. 1 is a schematic perspective view of the present invention;
FIG. 2 is a schematic view of the deflection configuration of the present invention;
FIG. 3 is a schematic view of the present invention in a self-rotating configuration;
fig. 4 is a schematic view of the present invention in both deflected and autorotated configurations.
In the figure: 1. the system comprises a fixed platform, a first shared platform, a second shared platform, a 4-tail end platform, a 5-driving rod I, a 6-driven rod I, a 7-straight bevel gear I, a 8-straight bevel gear II, a 9-driving rod II, a 10-driven rod II, a 11-straight bevel gear III, a 12-straight bevel gear IV, a 13-driving rod III and a 14-driven rod III.
Detailed Description
In the schematic diagrams of the human-shaped robot waist joint based on the 3-RRR spherical parallel mechanism shown in fig. 1-4, the human-shaped robot waist joint comprises 3 parallel mechanism units with the same structure, the parallel mechanism units are parallel mechanisms with three rotational degrees of freedom, each parallel mechanism unit comprises a fixed platform, a shared platform, a tail end platform and three RRR serial branched chains which are connected with the fixed platform, the shared platform and the tail end platform and have the same structure and are uniformly distributed along the circumferential direction, each RRR serial branched chain comprises a driving rod, a driven rod and a straight bevel gear, wherein one end of a driving rod I5 in the first parallel mechanism unit is connected with the fixed platform 1 through a revolute pair R1, the other end of the driving rod I5 is connected with one end of a driven rod I6 through a revolute pair R2, and the other end of the driven rod I6 is fixedly connected with a straight bevel gear I7 and is connected with a shared platform I2 through a revolut; one end of a driving rod II 9 of the second parallel mechanism unit is fixedly connected with a straight bevel gear II 8 and is connected with a common platform I2 through a revolute pair R4, a straight bevel gear I7 is meshed with the straight bevel gear II 8, the other end of the driving rod II 9 is connected with one end of a driven rod II 10 through a revolute pair R5, and the other end of the driven rod II 10 is fixedly connected with a straight bevel gear III 11 and is connected with a common platform II 3 through a revolute pair; one end of a driving rod III 13 of the tail-end parallel mechanism unit is fixedly connected with a straight bevel gear IV 12 and is connected with a shared platform II 3 through a revolute pair R7, a straight bevel gear III 11 is meshed with the straight bevel gear IV 12, the other end of the driving rod III 12 is connected with one end of a driven rod III 14 through a revolute pair R8, and the other end of the driven rod III 14 is connected with a tail-end platform 4 through a revolute pair R9; the same parallel mechanism unit contains 9 revolute pairs in total, and the axes of the revolute pairs intersect at one point;
the two adjacent parallel mechanism units are divided into a preceding stage mechanism unit and a subsequent stage mechanism unit according to the motion output direction, a first common platform is a movable platform of a first stage parallel mechanism and a fixed platform of a second stage parallel mechanism, a second common platform is a movable platform of a second stage parallel mechanism and a fixed platform of a third stage parallel mechanism, a driving rod of the first stage parallel mechanism unit, a driven rod of the second stage parallel mechanism and a driving rod of the third stage parallel mechanism use connecting rods with the same structure and size, a driven rod of the first stage parallel mechanism unit, a driving rod of the second stage parallel mechanism and a driven rod of the third stage parallel mechanism use connecting rods with the same structure and size, the two structure and size can be the same or different, the symmetry of the preceding stage parallel mechanism and the subsequent stage parallel mechanism about the common platform is not influenced, and the coupling mode is that the preceding stage mechanism unit and the driving rod of the subsequent stage parallel mechanism unit are additionally arranged between the driven rod of the preceding stage mechanism unit and the subsequent stage mechanism unit The single-degree-of-freedom transmission mechanism can equally convert the angle change of the driven rod of the preceding mechanism unit into the angle change of the driving rod of the rear mechanism unit, the single-degree-of-freedom transmission mechanism is a gear transmission mechanism consisting of one straight bevel gear with the same parameters or two straight bevel gears with the same parameters, and the two straight bevel gears are fixedly connected with the driven rod of the preceding parallel mechanism unit and the driving rod of the rear parallel mechanism unit respectively.