CN107756378B - Plane three-degree-of-freedom rigid body motion tracking mechanism - Google Patents

Abstract

The invention discloses a plane three-degree-of-freedom rigid motion tracking mechanism, which comprises a base and eleven connecting rods, wherein six connecting rods and the base form a two-degree-of-freedom rotary type imitation graph mechanism, and the connecting rods are connected by adopting conventional revolute pairs. The rigid body motion tracking mechanism is symmetrical about the hinge point O on the base as a whole, and the position and posture of the link 10 and the position and posture of the link 12 are also always symmetrical about the hinge point O. The invention has simple structure and good symmetry, and can be used for constructing a leg mechanism of a multi-foot robot or a multi-degree-of-freedom remote movement center mechanism in a medical robot.

Description

A planar three-degree-of-freedom rigid body motion tracking mechanism

Technical Field

The invention relates to a planar three-degree-of-freedom rigid body motion tracking mechanism, belonging to the field of mechanism design.

Background technique

If the motion of a component in a mechanism can track the rigid motion of another component in the mechanism, or in other words, the positions and postures of the two components in the mechanism always maintain a fixed simple mapping relationship (such as translation, rotation, reflection, etc.), then the mechanism can be called a rigid motion tracking mechanism. Rigid motion tracking mechanisms can be applied to the leg mechanisms of multi-legged robots to achieve gait synchronization or a fixed phase difference between multiple legs, and can also be used to construct multi-degree-of-freedom remote motion center mechanisms in medical robots.

The planar rigid body motion tracking mechanism can be constructed by combining two plotter mechanisms. A plotter mechanism is a drawing linkage mechanism that can perform simple transformations (such as translation, rotation, scaling, etc.) on graphics. Many scholars have studied the construction and application of plotter mechanisms and applied for relevant patents, such as CN 2013102733591 and CN2006101651217. A common plotter mechanism is the Sylvester five-bar plotter mechanism, as shown in Figure 1, which satisfies the following relationship: the quadrilateral ABDE formed by the connecting rods AB, BD, DE and EA is a parallelogram, and △BCD is similar to △EDF. Point C is the input point, and point E is the output point. The trajectory drawn by point C and the trajectory drawn by point E have the following relationship: the former is rotated around point A by an angle ∠EAB and enlarged by k=BD/BC times to obtain the latter.

The difference between the plotter mechanism and the rigid motion tracking mechanism is that the plotter mechanism is used to track the motion of a certain point, that is, the positions of two points on the mechanism always maintain a fixed simple mapping relationship; the rigid motion tracking mechanism is used to track the motion of a certain rigid body, that is, the positions and postures of the two rigid bodies on the mechanism always maintain a fixed simple mapping relationship. Due to this feature, the rigid motion tracking mechanism can be used for the leg mechanism and remote motion center mechanism of a multi-legged robot. The present invention constructs a planar three-degree-of-freedom rigid motion tracking mechanism based on the rotary plotter mechanism.

Summary of the invention

The invention provides a planar three-degree-of-freedom rigid body motion tracking mechanism based on a plotter mechanism, which has a simple and compact structure, has rotational symmetry, and can track any rigid body motion in a plane.

A planar three-degree-of-freedom rigid body motion tracking mechanism based on a plotter mechanism comprises a base (1) and eleven connecting rods, which are connected to each other by conventional revolute pairs, as shown in Figures 2 and 3. The eleven connecting rods are connecting rod 2, connecting rod 3, connecting rod 4, connecting rod 5, connecting rod 6, connecting rod 7, connecting rod 8, connecting rod 9, connecting rod 10, connecting rod 11 and connecting rod 12. Among them, connecting rod 2, connecting rod 3, connecting rod 4, connecting rod 5 form a parallelogram, and connecting rod 5, connecting rod 6, connecting rod 7, and connecting rod 2 also form a parallelogram, and these two parallelograms are always congruent. Connecting rod 2 and connecting rod 5 are connected at their respective midpoints by revolute pairs, and are connected to the base at this point by revolute pairs; connecting rod 8 is also connected to the base at its midpoint by revolute pairs; connecting rod 9 and connecting rod 11 are equal in length, and the positions of the hinges are also the same; connecting rod 10 and connecting rod 12 are equal in length, and the positions of the hinges are also correspondingly the same.

In the rigid body motion tracking mechanism, the connecting rods 2, 3, 4, 5, 6, 7 and the base together form a two-degree-of-freedom rotation type plotter mechanism, as shown in Figure 4. The motion characteristics of the plotter mechanism are: the line connecting the input point B and the output point E always passes through the fixed point O, and the distances from point B and point E to point O are always equal, that is, the input point B and the output point E are always symmetrical about the fixed point O.

In the rigid body motion tracking mechanism, the position and posture of the connecting rod 10 and the position and posture of the connecting rod 12 are always symmetrical about the fixed point O, that is, the connecting rod 12 always tracks the motion of the connecting rod 10. The connecting rod 10 or the connecting rod 12 in the mechanism of the present invention can perform any planar motion.

If a revolute pair is added to the end point I of the connecting rod 10 to connect the base, the connecting rod 10 will rotate around I, and the connecting rod 12 will also rotate around the fixed point L accordingly, with a phase angle difference of 180 degrees. At this time, the mechanism is a remote motion center mechanism; if the connecting rod 10 performs translational motion, the connecting rod 12 also performs translational motion in the opposite direction. That is, the motion of the connecting rod 10 and the connecting rod 12 is always symmetrical about the fixed point O.

Since this rigid body motion tracking mechanism has symmetry about the fixed hinge point O, the static balance of the mechanism can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the Sylvester plotter mechanism.

FIG. 2 is a three-degree-of-freedom rigid body motion tracking mechanism of the present invention.

FIG. 3 shows another state of the three-degree-of-freedom rigid body motion tracking mechanism of the present invention.

FIG. 4 is a diagram showing a two-degree-of-freedom imaging device included in the three-degree-of-freedom rigid body motion tracking device of the present invention.

1-base, 2-connecting rod 2, 3-connecting rod 3, 4-connecting rod 4, 5-connecting rod 5, 6-connecting rod 6, 7-connecting rod 7, 8-connecting rod 8, 9-connecting rod 9, 10-connecting rod 10, 11-connecting rod 11, 12-connecting rod 12.

Detailed ways

The present invention is further described in detail below in conjunction with the accompanying drawings.

As shown in Figures 2 and 3, the present invention is a planar three-degree-of-freedom rigid motion tracking mechanism, including a base and eleven connecting rods, the eleven connecting rods are connecting rod 2, connecting rod 3, connecting rod 4, connecting rod 5, connecting rod 6, connecting rod 7, connecting rod 8, connecting rod 9, connecting rod 10, connecting rod 11 and connecting rod 12. In this rigid motion tracking mechanism, connecting rod 2, connecting rod 3, connecting rod 4, connecting rod 5, connecting rod 6, connecting rod 7 and the base together constitute a two-degree-of-freedom rotation type plotter mechanism, as shown in Figure 4. Its input point is B and its output point is E. Connecting rod 2 and connecting rod 5 are connected by a revolute pair at their respective midpoints, and are connected to the base by a revolute pair at this point (i.e., point O), and other connecting rods are also connected by conventional revolute pairs. Each rod in the plotter mechanism satisfies the following relationship: AB∥CD∥FE, BC∥AF∥DE. Therefore, these six connecting rods constitute parallelogram ABCO and parallelogram ODEF. The motion characteristics of the plotter mechanism are as follows: the line connecting the input point B and the output point E always passes through the fixed point O, and the distances from point B and point E to point O are always equal, that is, the input point B and the output point E are always symmetrical about the fixed point O. Therefore, the figure drawn by the input point B rotates 180 degrees around point O to obtain the figure drawn by point E.

The present invention adds connecting rods 8, 9, 10, 11 and 12 and several revolute pairs on the basis of the above-mentioned plotter mechanism. The connecting rod 8 is connected to the base through a revolute pair at its midpoint. The connecting rods 9, 10, 11 and 12 also satisfy the following relationship: GH = JK, HB = KE, BI = EL. Therefore, the end point I of the connecting rod 10 and the end point L of the connecting rod 12 are always symmetrical about the fixed point O, and the position and posture of the connecting rod 10 and the position and posture of the connecting rod 12 are also always symmetrical about the fixed point O, that is, the connecting rod 12 always tracks the movement of the connecting rod 10. The connecting rod 10 or the connecting rod 12 in the mechanism of the present invention can make any planar motion.

Claims (2)

1. A plane three-degree-of-freedom rigid body motion tracking mechanism is characterized in that: the mechanism comprises a base (1) and eleven connecting rods, wherein the eleven connecting rods are respectively a connecting rod 2, a connecting rod 3, a connecting rod 4, a connecting rod 5, a connecting rod 6, a connecting rod 7, a connecting rod 8, a connecting rod 9, a connecting rod 10, a connecting rod 11 and a connecting rod 12; the connecting rod 2, the connecting rod 3, the connecting rod 4 and the connecting rod 5 form a parallelogram, the connecting rod 5, the connecting rod 6, the connecting rod 7 and the connecting rod 2 form a parallelogram, and the two parallelograms are congruent; the connecting rod 2 and the connecting rod 5 are connected at the respective midpoints by a revolute pair, and are connected with the base by the revolute pair at the point, wherein the point is a fixed hinge fulcrum O; the connecting rod 2, the connecting rod 3, the connecting rod 4, the connecting rod 5, the connecting rod 6 and the connecting rod 7 form a two-degree-of-freedom rotary imitation graph mechanism together with the base; the connecting rod 8 is also connected with the base at the middle point thereof through a revolute pair; the connecting rod 9 is connected with the connecting rod 8 at one end through a revolute pair, the connecting rod 11 is connected with the connecting rod 8 at the other end through a revolute pair, and the lengths of the connecting rod 9 and the connecting rod 11 are equal; the connecting rod 10 is connected with the connecting rod 9 at the end part through a revolute pair, and the connecting rod 12 is connected with the connecting rod 11 at the end part through a revolute pair; the connecting rods 10, 3 and 4 are hinged on the common point B, and the connecting rods 12, 6 and 7 are hinged on the common point E; the length of the connecting rod 10 is equal to that of the connecting rod 12, and the distance from the end part to the position of the hinge is also equal; when the link 10 is driven externally to perform any planar rigid motion, the link 12 correspondingly performs a similar planar rigid motion.

2. The planar three degree of freedom rigid motion tracking mechanism of claim 1 wherein the end point I of the link 10 and the end point L of the link 12 in the mechanism are always symmetrical about the fixed pivot point O, and the position and posture of the link 10 and the position and posture of the link 12 are also always symmetrical about the fixed pivot point O.