Three-degree-of-freedom mechanical arm driven based on spherical parallel mechanism
Technical Field
The invention relates to a mechanical arm, in particular to a three-degree-of-freedom mechanical arm driven by a spherical parallel mechanism.
Background
Present arm is mostly series structure. Although the series structure has a large movement range, each motor is a driving device of the next joint and a load of the previous joint, so that the end load capacity is low; the rotation errors of each motor in the series structure are in addition relation, so that the tail end movement error is large; and each joint is provided with a motor, so that the rigidity of the whole structure is low. The driving modes of the mechanical arm are generally divided into direct driving, rope driving, belt driving, gear driving and the like, the rope driving has the advantages of light weight, high movement speed and the like, but the load capacity is limited by the strength of the rope, the structural rigidity is low, and the winding is complicated; although the belt transmission and the gear transmission increase the joint torque by using the reduction ratio, the weight of the joint is increased due to the addition of the pulley and the gear, so that the actual improvement degree of the joint torque is limited.
Disclosure of Invention
The invention provides a three-degree-of-freedom mechanical arm based on a spherical parallel mechanism to overcome the defects of the prior art. The mechanical arm adopts a spherical parallel mechanism to drive the connecting rod mechanical arm, and the three motors are arranged at the shoulders in order, so that the weight of the arm is greatly reduced. Aiming at the problems of low load capacity, large motion error, low structural rigidity and the like of the existing series structure, the three-freedom-degree spherical parallel manipulator disclosed by the invention is provided with at least two motors for bearing when performing motion of each degree of freedom, and in the working process, the three motors perform torque distribution to drive three joints, so that the tail end load capacity is strong; the mechanical arm is formed by connecting rods made of light materials, so that the movement inertia is small, and the control difficulty is low; the rotation errors of each motor are not superposed, and the motion precision is high.
The technical scheme adopted by the invention is as follows: a three-degree-of-freedom mechanical arm based on spherical parallel mechanism driving comprises a three-degree-of-freedom spherical parallel driving device and a connecting rod arm; the three-degree-of-freedom spherical parallel driving device comprises a left motor, a right motor and a middle motor which are coaxial; the output end of the left motor is connected with a left transmission rod through a left output connecting rod; the output end of the right motor is connected with a right transmission rod through a right output connecting rod; the left transmission rod is hinged with the right transmission rod; the intermediate motor has an intermediate output link;
the axle center of left motor and right motor output end, left output connecting rod and left transfer line pin joint, right output connecting rod and right transfer line pin joint and left transfer line and right transfer line pin joint are located same sphere.
The connecting rod arm comprises a large arm rod, an elbow joint connecting piece, a small arm rod and a transmission arm rod; the transmission arm rod is hinged with the hinged ends of the left transmission rod and the right transmission rod through a transmission shaft; the large arm rod is connected with the middle output connecting rod through a rotating shaft. The big arm rod and the transmission arm rod are hinged to the elbow joint connecting piece, and the elbow joint connecting piece is fixedly connected with the small arm rod.
Furthermore, the three-degree-of-freedom spherical parallel driving device further comprises a left motor mounting plate, a left motor protective shell, a right motor mounting plate, a right motor protective shell, a middle motor mounting plate, a middle motor protective shell and a motor support frame;
the fixed ends of the left motor, the right motor and the middle motor are respectively arranged on the left motor protective shell, the right motor mounting plate and the middle motor mounting plate; the left motor protective shell, the right motor protective shell and the middle motor protective shell are respectively arranged on the left motor mounting plate, the right motor mounting plate and the middle motor mounting plate; the left motor mounting plate, the right motor mounting plate and the middle motor mounting plate are mounted on the motor support frame.
Furthermore, the connecting rod arm also comprises a fixing plate, a fixing seat, a mounting seat, a large arm rod mounting plate, a small arm fixing plate, a transmission arm mounting plate and a small arm transmission part;
one end of the rotating shaft is fixed in the two fixing plates, and the other end of the rotating shaft is arranged in the fixing seat; the fixed plate is arranged in the fixed seat; one end of the large arm rod is arranged on the fixed seat, and the other end of the large arm rod is arranged on the large arm rod mounting plate; the large arm rod mounting plate is connected with the elbow joint connecting piece; the elbow joint connecting piece is connected with the forearm transmission piece and is fixedly connected with the forearm mounting plate; one end of the small arm rod is arranged on the small arm mounting plate, and the other end of the small arm rod is arranged on the small arm fixing plate; the transmission shaft is connected with the transmission arm mounting plate; one end of the transmission arm rod is arranged on the transmission arm mounting plate, and the other end of the transmission arm rod is arranged on the small arm transmission part.
Furthermore, the elbow joint connecting piece is fixedly connected with the small arm mounting plate through a D-shaped shaft.
Furthermore, both ends of the D-shaped shaft are D-shaped, the middle of the D-shaped shaft is circular, and the fixing connection of the forearm mounting plate and the elbow joint connecting piece and the hinging connection of the forearm transmission piece and the elbow joint connecting piece are conveniently and simultaneously realized.
Compared with the prior art, the invention has the beneficial effects that:
(1) the method of driving the connecting rod mechanical arm by adopting the spherical parallel mechanism has the advantages that at least two motors are jointly driven when the mechanical arm moves in each degree of freedom, and the load capacity is greatly improved.
(2) The rotation errors of the motors are not overlapped, so that the motion precision of the arms is improved, the precision requirement on the motors is relaxed while the required motion precision is ensured to a certain extent, and the manufacturing cost is reduced.
(3) All motors are placed at shoulder joints, and the connecting rod mechanical arm is made of light materials such as aluminum alloy and carbon fiber, so that the weight of the connecting rod mechanical arm is greatly reduced, the motion inertia is reduced, and the driving difficulty is reduced.
(4) The connecting rod arm adopts the design of four-bar structure, has improved whole rigidity.
Drawings
FIG. 1 is an isometric view of an entirety of a three-degree-of-freedom spherical parallel mechanical arm;
FIG. 2 is an isometric view of a three-degree-of-freedom spherical parallel driving device;
FIG. 3 is a three-dimensional view of a three-degree-of-freedom spherical parallel driving device;
FIG. 4 is an isometric view of the link arm;
FIG. 5 is an enlarged view of a portion of the joint between the boom and the drive mechanism;
FIG. 6 is an enlarged partial view of the joint between the upper and lower arms;
FIG. 7 illustrates various motor placement patterns;
FIG. 8 shows a preferred motor matching method according to the work content;
FIG. 9 shows a large arm, a small arm and a driving arm which are integrally formed;
in the figure: 1. the three-degree-of-freedom spherical parallel driving device comprises a three-degree-of-freedom spherical parallel driving device 2, a connecting rod arm 110, a left motor mounting plate 111, a left motor 112, a left output connecting rod 113, a left motor protective shell 114 and a left transmission rod; 120. the right motor mounting plate 121, the right motor 122, the right output connecting rod 123, the right motor protective shell 124 and the right transmission rod; 130. the motor comprises a middle motor mounting plate, a middle motor, a middle output connecting rod 132, a middle motor protective shell 133, a middle motor supporting frame 134 and a motor supporting frame; 210. the device comprises a rotating shaft, 211, a fixing plate, 212, a fixing seat, 213, a mounting seat, 214, a big arm rod, 215, an elbow joint connecting piece, 216, a big arm rod mounting plate, 221, a small arm mounting plate, 222, a small arm rod, 223, a small arm fixing plate, 231, a transmission shaft, 232, a transmission arm mounting plate, 233, a transmission arm rod, 234 and a small arm transmission piece.
Detailed Description
The invention is further illustrated by the following figures and examples.
As shown in fig. 1, the present invention provides a three-degree-of-freedom mechanical arm driven by a spherical parallel mechanism, which includes a three-degree-of-freedom spherical parallel driving device 1 and a connecting rod arm 2;
the output end of the three-degree-of-freedom spherical parallel driving device 1 is connected with a connecting rod arm 2 which is driven by the driving device to rotate.
As shown in fig. 2 and fig. 3, the three-degree-of-freedom spherical parallel driving device 1 includes a left motor 111, a left motor mounting plate 110, a left motor protective housing 113, a left output link 112, a left transmission rod 114, a right motor 121, a right motor mounting plate 120, a right motor protective housing 123, a right output link 122, a right transmission rod 124, an intermediate motor 131, an intermediate motor mounting plate 130, an intermediate motor protective housing 133, an intermediate output link 132, and a motor support frame 134; the fixed end of the left motor 111 and the left motor protective shell 113 are fixed through screws, and the output end of the left motor 111 and the left output connecting rod 112 are fixed through screws; the left output link 112 is connected with a left transmission rod 114; the left motor protective shell 113 and the left motor mounting plate 110 are fixed through screws; the fixed end of the right motor 121 and the right motor mounting plate 120 are fixed through screws; the output end of the right motor 121 and the right output connecting rod 122 are fixed through screws; the right output link 122 is connected with a right transmission rod 124; the right motor protective shell 123 and the right motor mounting plate 120 are fixed through screws; the left driving rod 114 is hinged with the right driving rod 124; the fixed end of the middle motor 131 and the middle motor mounting plate 130 are fixed by screws; the output end of the intermediate motor 131 and the intermediate output connecting rod 132 are fixed by screws; the middle motor protective shell 133 and the middle motor mounting plate 130 are fixed by screws; the left motor mounting plate 110, the right motor mounting plate 120 and the middle motor mounting plate 130 are fixed with the motor support bracket 134 by screws.
As shown in fig. 3, the left motor 111, the right motor 121, the left output link 112, the right output link 122, the left transmission rod 114, and the right transmission rod 124 of the three-degree-of-freedom spherical parallel driving device 1 together form a spherical parallel mechanism, and the three motors are coaxially and equidirectionally disposed. The axes of the output ends of the left motor 111 and the right motor 121, the hinge point of the left output link 112 and the left transmission rod 114, the hinge point of the right output link 122 and the right transmission rod 124, and the hinge point of the left transmission rod 114 and the right transmission rod 124 are located on the same spherical surface. As a preferable scheme of the above scheme, the three motors may also be placed in a manner as shown in fig. 7, the orientation of the middle motor 131 is unchanged, the output ends of the left motor 111 and the right motor 121 are oriented to be uniformly outward or uniformly inward, and the connection relationship between the components is unchanged, such a placement manner can make the structure symmetrical, and the stress of the connecting rod is also more uniform.
Preferably, according to the specific work content of the mechanical arm, motors with different output torques can be adopted to form the three-degree-of-freedom spherical parallel driving device 1. For example, if the work content requires a large load when the lower arm lever is lifted, the left motor 111 and the right motor 121 having a large output torque and the middle motor having a relatively small output torque may be used, as shown in fig. 8. Therefore, the best motor collocation can be selected according to the working content, the motor torque is reasonably distributed, and the performance of the motor is fully exerted.
As shown in fig. 4, 5 and 6, the link arm 2 includes a rotation shaft 210, a fixing plate 211, a fixing base 212, a mounting base 213, a large arm lever 214, a large arm lever mounting plate 216, a toggle joint 215, a small arm mounting plate 221, a small arm lever 222, a small arm fixing plate 223, a transmission shaft 231, a transmission arm mounting plate 232, a transmission arm lever 233 and a small arm transmission member 234; two identical fixing plates 211 are fixed by screws and fix one end of the rotation shaft 210; the other end of the rotating shaft 210 is installed in the installation seat 213; the fixed seat 212 is mounted on the mounting seat 213 through a screw, and the fixed seat 212 can axially rotate around the rotating shaft 210 relative to the fixed plate 211; one end of the upper arm lever 214 is mounted on the fixing base 212 by a screw, and the other end is mounted on the upper arm lever mounting plate 216 by a screw. Preferably, the large arm rod 214 is made of light materials such as carbon fiber square tubes, so as to reduce the weight of the arm and reduce the inertia of the arm. The upper arm lever mounting plate 216 is connected with the elbow joint connecting piece 215 through a hinge; the elbow joint connecting piece 215 is fixedly connected with the forearm mounting plate 221 through a D-shaped shaft; one end of the small arm rod 222 is mounted on the small arm mounting plate 221 through a screw, and the other end is mounted on the small arm fixing plate 223 through a screw; one end of the transmission shaft 231 is connected with the hinged ends of the left transmission rod 114 and the right transmission rod 124 through hinges, and the other end is connected with the transmission arm mounting plate 232 through hinges; one end of the transmission arm lever 233 is mounted on the transmission arm mounting plate 232 by a screw, and the other end is mounted on the small arm transmission member 234 by a screw; forearm drive member 234 is hingedly connected to elbow joint 215. Preferably, the "D" shaft is formed with two ends "D" and a middle circular shape to facilitate the fixation of the forearm mounting plate 221 and the elbow joint connector 215 and the articulation of the forearm drive member 234 and the elbow joint connector 215.
Preferably, as shown in fig. 9, the mounting seat 213, the upper arm lever 214, the upper arm lever mounting plate 216, the lower arm mounting plate 221, the lower arm fixing plate 223, the lower arm lever 222, the transmission arm mounting plate 232, the transmission arm lever 233, and the lower arm transmission member 234 may be integrally formed by using pre-embedded metal parts, bonding, and the like, so as to not only simplify the structure, but also eliminate the machining error and the assembly error caused by machining and mechanical connection, and improve the overall motion accuracy of the mechanical arm.
The beneficial technical effects of the specific embodiment are as follows: the rotation of the three coaxial motors is synthesized by the motion of the spherical parallel mechanism and converted into three motions of large arm rotation, small arm rotation and arm axial rotation. When the middle motor 131, the left motor 111 and the right motor 121 rotate in the same direction and the same moment, the large arm rod 214 rotates, and the small arm rod 222 does not rotate; when the middle motor 131 does not rotate and the left motor 111 and the right motor 121 rotate in the same direction and the same moment, the large arm rod 214 does not rotate and the small arm rod 222 rotates; when the middle motor 131 does not rotate, and the left motor 111 and the right motor 121 rotate reversely and with the same torque, the large arm rod 214 and the small arm rod 222 axially rotate.
Principle of operation
Referring to fig. 1 to 7, three motors which are coaxial are used as shoulder joints, the left motor 111, the right motor 121 and the middle motor 131 rotate in the same direction by the same angle to drive the whole connecting rod arm 2 to rotate around the shoulder joints, so that the degree of freedom of lifting the big arm is achieved, and the output torque directions of the three motors are the same as the rotation directions of the big arm and are mutually accumulated; when the left motor 111 and the right motor 121 rotate in the same direction by the same angle and the middle motor 131 is not moved, the large arm lever 214 is not moved, and the small arm lever 222 is driven by the transmission arm lever 233 to rotate, so that the degree of freedom of lifting the small arm is completed, and at the moment, the output torque directions of the two motors are the same as the rotation direction of the small arm and are mutually accumulated; when the left motor 111 and the right motor 121 rotate in opposite directions by different angles and the middle motor 131 is not moved, the connecting rod arm 2 rotates around its own rotation axis, thereby completing the degree of freedom of the axial rotation of the arm.
The above-described embodiments are intended to illustrate rather than to limit the invention, and all modifications and variations that fall within the spirit of the invention and the scope of the appended claims are intended to be embraced thereby.