CN115366070A - Parallel six-degree-of-freedom motion platform with variable rigidity and stroke and motion control method thereof - Google Patents

Abstract

The invention relates to the technical field of multi-degree-of-freedom motion platforms, and provides a parallel type six-degree-of-freedom motion platform with variable rigidity and stroke and a motion control method thereof.

Description

Parallel six-degree-of-freedom motion platform with variable rigidity and stroke and motion control method thereof

Technical Field

The invention relates to the technical field of six-degree-of-freedom motion platforms, in particular to a parallel type six-degree-of-freedom motion platform with variable rigidity and stroke and a motion control method thereof.

Background

A parallel six-degree-of-freedom motion platform (a six-degree-of-freedom parallel robot) is a structural design of a Stewart platform, can simulate motion postures of multiple degrees of freedom in space by driving an electric cylinder to move, and is widely applied to various training simulators, such as flight simulators, automobile driving simulators, earthquake simulators, aircrafts such as satellites and guided missiles, and the like, and the fields of entertainment equipment (dynamic movie swinging platforms).

The parallel six-freedom-degree motion platform is a 6-shaped parallel mechanism consisting of an upper platform, a lower platform, 6 electric cylinders in the middle and 6 hooke joints (or spherical joints) respectively arranged at the upper part and the lower part, wherein the lower platform is fixed, the lower platform is connected with the upper platform through the 6 electric cylinders and the hooke joints, and the hooke joints or the spherical joints are positioned at the joints of the upper platform and the 6 electric cylinders, so that the parallel six-freedom-degree motion platform plays a key role in ensuring the normal operation of the platform and the rigidity of the whole structure. The translation of the upper platform along X, Y and Z and the rotation motion around X, Y and Z axes are realized by the extension and contraction of each electric cylinder.

Generally, a parallel six-degree-of-freedom motion platform is driven by a servo electric cylinder, and certainly, a hydraulic cylinder is adopted in the design of a heavy-load parallel six-degree-of-freedom motion platform. The motion of the upper platform in six degrees of freedom (X, Y, Z, alpha, beta, gamma) in space is driven by controlling the telescopic motion of the six electric cylinders, so that various spatial motion postures can be simulated, the corresponding position and speed instruction signals of each electric cylinder are calculated according to the motion state of the six-degree-of-freedom platform in the motion process, the motion of the motion platform is controlled, the motion according to a preset track is ensured, when the motion platform reaches a required position, the speed instruction signals of each electric cylinder are given to be zero, the motion platform stops, and the purpose of point position control is achieved. Meanwhile, a closed-loop control strategy is adopted in the motion process, the speed and displacement signals of each electric cylinder are fed back, the speed signals are used for inputting the tracking speed in the closed-loop control, and the displacement signals are used for position feedback and monitoring, so that the aim of meeting the pose control of the motion platform is fulfilled.

The parallel six-degree-of-freedom motion platform is driven by 6 servo electric cylinders arranged in parallel, has the advantages of high transmission efficiency, high speed, strong load capacity, high rigidity and high precision, and is more and more widely applied to various industries. Indexes such as load capacity, motion space, motion speed and acceleration of the parallel six-degree-of-freedom motion platform are difficult to consider in all aspects, if the motion space is pursued to be large, the load capacity needs to be sacrificed, and if the transverse displacement acceleration is pursued to be large, the rotation angular acceleration needs to be sacrificed. Moreover, the performance indexes of the parallel robot are already set after the overall design of the parallel robot is determined, so that the work task of a parallel six-degree-of-freedom motion platform is single. Under complex working conditions, a parallel six-degree-of-freedom motion platform is difficult to meet the left-right working requirements, the parallel robot needs to be good in transverse displacement rigidity or large in translation stroke, needs to be designed to be short, and the included angle between an electric cylinder and the ground is small; the rotating rigidity is required to be good or the rotating angle is required to be large, the design is required to be higher, and the included angle between the electric cylinder and the ground is larger. Or the stroke of the electric cylinder is changed to improve the performance indexes. When interference occurs in a certain pose, no other method for avoiding interference is available except for limiting the travel of the pose.

For example, as shown in fig. 1, when the lateral component force is small, the horizontal movement capability and the lateral stiffness of the upper platform are not ideal, and when the lateral component force is increased, the horizontal movement force output capability and the lateral stiffness are improved. Referring to fig. 2, when the lateral component force is small and the α and β moment arms are large, the rotational stiffness is good, but when the lateral component force is increased, the α and β moment arms are reduced, which leads to a problem of reduced rotational capability.

In addition, the structural interference and position singularity problems shown in fig. 3a and 3b are also a big problem in the design and use of the current six-degree-of-freedom parallel robot, such as the structural interference between the upper platform and the electric cylinder and the interference between the hinge and the electric cylinder shown in fig. 3, and the structural interference problem belongs to a design defect problem, which can cause serious damage to the electric and moving platforms, and is not allowed to occur, while in the design of the large-tonnage heavy-load six-degree-of-freedom parallel robot, the structural interference can also be a serious safety accident, which is not desired or allowed to occur.

Disclosure of Invention

The swing arm mechanism is provided with two rotary joints which are respectively driven by a motor and a speed reducer, so that the layout of a lower hinge point is changed, the diameter of a hinge circle and the inclination angle of an electric cylinder are changed, the rotary rigidity, the transverse translational rigidity and the strokes in all directions of the platform are changed, and the structural interference is avoided.

As a second aspect of the present invention, the present invention provides a swing arm motion of a parallel six-degree-of-freedom motion platform with variable stiffness and stroke, and controls two working modes of the parallel six-degree-of-freedom motion platform:

in a first mode: the diameter of the lower hinge circle is changed through the movement of the swing arm mechanism, and the expansion amount of the electric cylinder is unchanged; in the motion driving process, the diameter of the lower hinge circle is changed by driving the six swing arm mechanisms to do the same motion;

in a second mode: the motion platform is fixed, changes the flexible volume of one or more electronic jar through the motion of swing arm mechanism.

Therefore, under two modes, the rotation rigidity, the transverse translation rigidity and the strokes in all directions of the platform can be changed through the adjustment of the two rotation joints, and the structural interference is avoided.

The invention provides a control method of a parallel six-degree-of-freedom motion platform with variable rigidity and stroke, which comprises the following steps:

firstly, defining a coordinate system: setting the center point of the upper plane of the base as O, establishing a global coordinate system CoordOXYZ on the upper plane of the center of the base, and establishing a local coordinate system CoordA at the center of the hole of the connecting lug of the ith base _i X _i1 Y _i1 Z _i1 Establishing a local coordinate system CoordB at the center of the connecting lug seat hole of the ith lower hook hinge base _i X _i2 Y _i2 Z _i2 ；

Solving a hinge point C by acquiring the motion angles of two joints of the swing arm mechanism _i In a local coordinate system CoordB _i X _i2 Y _i2 Z _i2 The coordinates of (a); hinge point B _i CoordA in local coordinate system _i X _i1 Y _i1 Z _i1 Can obtain the coordinates ofTo the local coordinate system CoordB _i X _i2 Y _i2 Z _i2 And local coordinate system CoordA _i X _i1 Y _i1 Z _i1 The conversion relationship of (1).

Wherein the hinge point C _i The coordinates of (A) can be converted into a local coordinate system CoordA through coordinate system conversion _i X _i1 Y _i1 Z _i1 (ii) a Due to the local coordinate system CoordA _i X _i1 Y _i1 Z _i1 The transformation relationship with the global coordinate system coordoyx is fixed and known, so the hinge point C _i May be further converted into coordinates of a global coordinate system coordoyx.

Therefore, in the first mode, the upper platform changes the height along with the movement of the swing arm mechanism, but the upper platform keeps horizontal, the X coordinate and the Y coordinate of the upper hinge point are unchanged, and the Z coordinate can be obtained through solving. In the second mode, the coordinates of the upper platform hinge point are unchanged.

Compared with the prior art, the parallel six-degree-of-freedom motion platform and the motion control method thereof provided by the invention have the advantages that the swing arm mechanism is additionally arranged at the bottom of the electric cylinder of the six-degree-of-freedom motion platform, and the swing arm mechanism is provided with two rotary joints which are respectively driven by the motor and the speed reducer. Through the motion of the swing arm mechanism, the diameter of the hinged circle and the inclination angle of the electric cylinder are changed, so that the rotation rigidity, the transverse translation rigidity and the strokes in all directions of the platform are changed, the structural interference is avoided, and the stability, the reliability, the safety and the application range of the platform motion are improved.

It should be understood that all combinations of the foregoing concepts and additional concepts described in greater detail below can be considered as part of the inventive subject matter of this disclosure unless such concepts are mutually inconsistent. In addition, all combinations of claimed subject matter are considered a part of the presently disclosed subject matter.

The foregoing and other aspects, embodiments and features of the present teachings can be more fully understood from the following description taken in conjunction with the accompanying drawings. Additional aspects of the present invention, such as features and/or advantages of exemplary embodiments, will be apparent from the description which follows, or may be learned by practice of specific embodiments in accordance with the teachings of the present invention.

Drawings

The figures are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. Embodiments of various aspects of the present invention will now be described, by way of example, with reference to the accompanying drawings, in which:

fig. 1 is a schematic diagram of a prior art platform before and after adjustment of a lateral force component.

Fig. 2 is a schematic diagram of a platform before and after adjustment of the rotating moment arms in the alpha and beta directions in the prior art.

Fig. 3a and 3b are schematic diagrams illustrating the structural interference of a parallel six-degree-of-freedom motion platform in the prior art, wherein fig. 3a shows the structural interference between an upper platform and an electric cylinder, and fig. 3b shows the structural interference between a hinge and the electric cylinder.

FIG. 4 is a schematic diagram of a parallel six-degree-of-freedom motion platform with variable stiffness and stroke according to an embodiment of the invention.

Fig. 5 is a schematic diagram of a swing arm mechanism in the parallel type six-degree-of-freedom motion platform of the embodiment of fig. 4.

Fig. 6 is a schematic diagram of coordinate system definition of the parallel six-degree-of-freedom motion platform of the embodiment of fig. 4.

Fig. 7 is an axonometric view of the initial position state of the parallel six-degree-of-freedom motion platform of the embodiment of fig. 4.

Fig. 8 is a schematic diagram of the lower hinge circle of the parallel six-degree-of-freedom motion platform in an expanded state in the embodiment in fig. 4.

Fig. 9 is an isometric view of the parallel six-degree-of-freedom motion platform of the example lower articulated circle of fig. 8 in an expanded state.

Fig. 10 is a schematic view of a reduced lower hinge circle of the parallel six-degree-of-freedom motion platform of the embodiment of fig. 4.

Fig. 11 is an isometric view of the parallel six degree-of-freedom motion platform of the example lower articulated circle of fig. 10 in a reduced state.

Detailed Description

In order to better understand the technical content of the present invention, specific embodiments are described below with reference to the accompanying drawings.

In this disclosure, aspects of the present invention are described with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. Embodiments of the present disclosure are not necessarily intended to include all aspects of the invention. It should be appreciated that the various concepts and embodiments described above, as well as those described in greater detail below, may be implemented in any of numerous ways, as the disclosed concepts and embodiments are not limited to any one implementation. In addition, some aspects of the present disclosure may be used alone, or in any suitable combination with other aspects of the present disclosure.

Referring to fig. 4 to 6, a parallel type six-degree-of-freedom motion platform according to the embodiment of the present disclosure includes a base 100, a motion platform 200, and an electric cylinder 400 disposed between the base 100 and the motion platform 200. Each electric cylinder 400 is provided with an independent or centralized control panel and a driving program, and is used for controlling the telescopic motion of the electric cylinder 400 to drive the multi-degree-of-freedom attitude adjustment of the motion platform 200, thereby realizing the multi-degree-of-freedom motion simulation.

The parallel six-degree-of-freedom motion platform shown in fig. 4 further includes upper hooke's hinge bases 600 disposed on the lower bottom surface of the motion platform 200, correspondingly, each upper hooke's hinge base 600 is correspondingly provided with a lower hooke's hinge base 300, the lower hooke's hinge base 300 is correspondingly supported on the upper end of the swing arm mechanism, and the lower end of the swing arm mechanism is supported on the upper surface of the base 100.

With reference to fig. 4, 5, and 6, the six electric cylinders 400 are respectively provided with the corresponding upper hooke joint base 600, lower hooke joint base 300, and swing arm mechanisms, and the upper and lower ends of each electric cylinder 400 are hinged between the corresponding upper hooke joint base 600 and lower hooke joint base 300.

In connection with the example shown in fig. 4 and 5, a first ear mount 310 is provided below the lower hooke's hinge base 300. Accordingly, the upper surface of the base 100 is provided with the second ear mount 110 corresponding to the lower hooke's joint base 300 of each electric cylinder. The first ear mount 310 is configured to mate with the second ear mount 110.

As shown in fig. 4 and 5, a swing arm mechanism is disposed below each electric cylinder 400 for expanding or contracting the lower hinge circle to change the rotational stiffness, the lateral translational stiffness, and the stroke in each direction of the platform, thereby avoiding structural interference.

The lower hinge circle in the embodiment of the invention is a hinge circle formed by a hinge point at the lower end of an electric cylinder, the diameter and the position of the lower hinge circle are determined by a hinge hooke hinge arranged on a lower platform in the traditional platform design with a fixed position, and are fixed and unchangeable, so that the problem that the lower hinge circle has rotating rigidity, transverse translational rigidity and strokes in all directions under complex working conditions exists as described in the background technology of the invention.

In an alternative embodiment, each swing arm mechanism is configured with two rotary joints, namely a first rotary joint (upper rotary joint) arranged at the first ear seat 310 and a second rotary joint (lower rotary joint) arranged at the second ear seat 110, each rotary joint is driven to rotate by a motor driving mechanism, so that the inclination angle of the electric cylinder and the diameter of the hinge circle are changed through the rotary motion of the two joints of the swing arm mechanism, and further the rotary rigidity, the transverse translational rigidity and the stroke in each direction of the platform are changed, and the structural interference is avoided.

As shown in fig. 4 and 5, a swing arm 530 is disposed between the two rotary joints of each swing arm mechanism, a first fork 531 is disposed at the upper end of the swing arm 530, and a second fork 532 is disposed at the lower end.

The first ear mount 310 is mounted inside the first fork 531.

The second ear mount 110 is mounted within the second prong 532.

In an alternative embodiment, the aforementioned motor drive mechanism includes a motor and a reduction mechanism. The motor and the reduction mechanism are coaxially arranged and are coaxially arranged with the corresponding first ear mount 310 or second ear mount 110. In an alternative embodiment, each reducer output is connected with a corresponding ear mount by a key connection.

Specifically, the motor driving mechanism disposed at the position of the first ear seat 310 includes a first motor 511 and a first speed reducer 512, the first motor 511 is a stepping motor, an output shaft thereof is connected with an input end of the first speed reducer 512, and the first speed reducer 512 is preferably a planetary gear speed reducer, an output end thereof is keyed to a rotation center of the first ear seat 310 to drive rotation, so as to adjust rotation of the first rotary joint.

In an alternative embodiment, the output shaft end of the first reducer 512 is keyed to the center of the first ear mount 310.

In the embodiment of the invention, the first rotary joint and the second rotary joint are both composed of corresponding ear seats and motor driving mechanisms, and the rotary driving of the joints is realized by matching with corresponding fork parts (531, 532).

As shown in fig. 4 and 5, the motor driving mechanism disposed at the second ear seat 110 includes a second motor 521 and a first speed reducer 522, the second motor 521 can be a stepping motor, an output shaft of the second motor is connected to an input end of the second speed reducer 522, and the second speed reducer 522 is preferably a planetary gear speed reducer, an output end of the planetary gear speed reducer is keyed to a rotation center of the second ear seat 110 to drive rotation, so as to adjust rotation of the second rotary joint.

In an alternative embodiment, the output shaft end of the second reducer 522 is keyed to the center of the first ear mount 310.

Referring to fig. 4 and 5, in the design of the two rotary joints, the output shaft end corresponding to each speed reducer passes through the side hole of the corresponding first fork 531 or second fork 532, and then is connected to the rotary center of the corresponding ear seat.

It should be understood that the rotary drive mechanism for the two rotary joints can be implemented using existing highly integrated drive mechanisms to implement a rotary drive design for joint positions under the teachings of the present invention.

Therefore, as shown in fig. 5 and 6, for the swing arm mechanisms corresponding to the six electric cylinders arranged on the platform, the first rotary joints and the second rotary joints are synchronously driven to keep the first rotary joints moving in the same way, and the second rotary joints moving in the same way, so that the diameter of the lower hinge circle is changed, and the expansion and contraction amount of the electric cylinders is unchanged, so that the diameter of the lower hinge circle is enlarged and reduced, the rotation rigidity, the transverse translation rigidity and the stroke adjustment in each direction are realized, the application under complex working conditions is adapted, and especially under the condition of large stroke in the horizontal transverse moving direction, the contradiction between the balance and the rotation rigidity and the rotation angle is balanced.

As shown in fig. 8 to 9, which are schematic diagrams illustrating an expanded state of the lower hinge circle of the parallel six-degree-of-freedom motion platform according to the embodiment of the present invention, by synchronously controlling the motion of the first rotating joints and the motion of the second rotating joints, such that the rotating speeds and the rotating angles of the 6 first rotating joints are consistent, and the rotating speeds and the rotating angles of the 6 second rotating joints are consistent, the tilt angle of the swing arm 530, that is, the tilt angle of the swing arm mechanism, is adjusted to expand towards the edge direction of the base 110, so as to adjust the tilt angle of the electric cylinder 400, and expand the lower hinge circle.

As shown in fig. 10 to 11, which are schematic diagrams illustrating a reduced lower hinge circle state of a parallel six-degree-of-freedom motion platform according to an embodiment of the present invention, by synchronously controlling the motion of the first rotary joints and the motion of the second rotary joints, such that the rotation speeds and rotation angles of the 6 first rotary joints are consistent, and the rotation speeds and rotation angles of the 6 second rotary joints are consistent, the tilt angle of the swing arm 530 is adjusted, and the swing arm is contracted toward the center origin of the base 110, so as to adjust the tilt angle of the electric cylinder 400, and reduce the lower hinge circle.

Based on the parallel type six-degree-of-freedom motion platform with variable rigidity and stroke and the motion control process thereof, which are provided by combining the examples shown in fig. 4 and fig. 7-11, the parallel type six-degree-of-freedom motion platform can be set into two working modes:

in the first mode: the diameter of the lower hinge circle is changed through the movement of the swing arm mechanism, and the expansion amount of each electric cylinder 400 is unchanged; in the process of motion driving, the diameter of the lower hinge circle is changed by driving the six swing arm mechanisms to do the same motion, as shown in fig. 8-9 and fig. 10-11, after the diameter of the lower hinge circle is adjusted, the attitude of the upper platform, namely the attitude of the motion platform 200, can be adjusted by driving the electric cylinder 400, so that the problem of contradiction between the rotational rigidity and the rotational angle and the traverse stroke is solved by controlling the motion attitude adjustment of the platform on the premise of enlarging or reducing the hinge circle;

in the second mode: the upper platform and the lower platform are kept fixed, and the stretching amount of one or more electric cylinders is changed through the movement of the swing arm mechanism.

In the design of the parallel six-degree-of-freedom motion platform, the practical process and test of the multi-degree-of-freedom platform are found that because the electric cylinder is usually determined according to design parameters, the larger the size difference between an upper hinged circle and a lower hinged circle of the parallel six-degree-of-freedom motion platform is, the larger the inclination angle of the electric cylinder is, the better the transverse rigidity is, and the worse the rotation rigidity is. Meanwhile, the length of the electric cylinder is fixed, the size difference between the upper hinge circle and the lower hinge circle of the parallel six-degree-of-freedom motion platform is larger, the larger the inclination angle of the electric cylinder is, the larger the translation stroke of the electric cylinder is, and the smaller the rotation stroke of the electric cylinder is.

According to the six-degree-of-freedom motion platform, the swing arm mechanism is additionally arranged at the bottom of the electric cylinder of the six-degree-of-freedom motion platform, the swing arm mechanism is provided with two rotary joints which are respectively driven by the motor and the speed reducer, so that the diameter of a hinged circle and the inclination angle of the electric cylinder are changed through the motion of the swing arm mechanism, the rotary rigidity, the transverse translational rigidity and the strokes in all directions of the platform are further changed, and the structural interference is avoided.

Therefore, the rotation rigidity, the transverse translation rigidity and the strokes in all directions of the platform can be changed through the adjustment of the two rotation joints, and the structural interference is avoided.

As a second aspect of the invention, the invention provides a control method of a parallel six-degree-of-freedom motion platform with variable rigidity and stroke, which is implemented by constructing the global coordinate of a plane on the center of a baseCoordoyx, lower local coordinate system CoordA at center of side hole of ith second ear mount on base _i X _i1 Y _i1 Z _i1 And an upper local coordinate system CoordB established at the center of the side hole of the ith first ear seat _i X _i2 Y _i2 Z _i2 And calculating the position coordinates of each hinge point in the motion state through the conversion and the reverse connection of the hinge point coordinate system.

As an alternative embodiment, the position coordinates of each hinge point in the motion state are calculated through the transformation and the reverse connection of the hinge point coordinate system, and the process comprises the following steps:

firstly, defining a coordinate system: setting the center point of the upper plane of the base as O, constructing a global coordinate system CoordOXYZ of the upper plane of the center of the base and a lower local coordinate system CoordA at the center of the side hole of the ith second ear seat on the base _i X _i1 Y _i1 Z _i1 And an upper local coordinate system CoorddB established at the center of the side hole of the ith first ear seat _i X _i2 Y _i2 Z _i2 ；

Solving a hinge point C by acquiring the motion angles of two rotary joints of the swing arm mechanism _i CoordB in the upper local coordinate system _i X _i2 Y _i2 Z _i2 Coordinates of (2), hinge point B _i In the lower local coordinate System CoordA _i X _i1 Y _i1 Z _i1 To obtain the upper local coordinate system CoordB _i X _i2 Y _i2 Z _i2 And the lower local coordinate system CoordA _i X _i1 Y _i1 Z _i1 The conversion relationship of (1).

Wherein the hinge point C _i Can be converted into a local coordinate system CoordA through coordinate system conversion _i X _i1 Y _i1 Z _i1 (ii) a Due to the lower local coordinate system CoordA _i X _i1 Y _i1 Z _i1 The transformation relationship with the global coordinate system coordoyx is fixed and known, so the hinge point C can be set _i May be further converted into coordinates of a global coordinate system coordoyx.

(1) Definition of coordinate system

Global seating for constructing upper plane of center of baseCoordinate system coordoyx, lower local coordinate system CoordA at center of side hole of ith second ear seat on base _i X _i1 Y _i1 Z _i1 And an upper local coordinate system CoordB established at the center of the side hole of the ith first ear seat _i X _i2 Y _i2 Z _i2 ；

(2) Setting initial state of platform

In connection with fig. 4, 6 and 7, in the initial position state, the hinge point C is a design parameter of the platform _i And hinge point D _i Coordinate of global coordinate system coordoyx, where CoordB is the local coordinate system _i X _i2 Y _i2 Z _i2 Is known; hinge point Bi under the local coordinate system CoordA _i X _i1 Y _i1 Z _i1 The coordinates of (a) are known.

Wherein the hinge point C _i The rotation center point of the bottom of the ith electric cylinder 400 and the corresponding ith lower hooke's joint base 300 is shown, and the lower hinge point is shown.

Hinge point D _i The rotation center point of the top of the ith electric cylinder 400 and the corresponding ith upper hooke's joint base 600 is shown, and the upper hinge point is shown.

Referring to fig. 6, the hinge point Bi represents a rotation center point of the first fork 531 and the corresponding first ear mount 310 of the swing arm in the swing arm mechanism corresponding to the ith electric cylinder 400.

The hinge point Ai represents a rotation center point of the second fork 532 of the swing arm in the swing arm mechanism corresponding to the ith electric cylinder 400 and the corresponding second ear seat 110. Since the second ear mount 110 is fixed to the base 100, the global coordinates of the hinge point Ai are known and remain unchanged.

Lower local coordinate system CoordA _i X _i1 Y _i1 Z _i1 Offset from the global coordinate system coordoyx [ delta ] X, [ delta ] Y, [ delta ] Z, [ delta ] α, [ delta ] β, [ delta ] γ [ ]]Are known.

(3) Hinge point coordinate transformation

As can be seen from fig. 4 and 6, the second rotary joint (i.e., the lower rotary joint) and the first rotary joint (i.e., the upper rotary joint) of the swing arm mechanism are respectively wound around two local coordinate systemsY of (A) is _i1 And Y _i2 Rotation, angle of rotation being respectively beta ₁ And beta ₂ 。

At the initial state, the hinge point B _i In the lower local coordinate System CoordA _i X _i1 Y _i1 Z _i1 Has the coordinates of (x) _i1 ，y _i1 ，z _i1 ) Hinge point C _i CoordB in the upper local coordinate system _i X _i2 Y _i2 Z _i2 Has the coordinates of (x) _i2 ，y _i2 ，z _i2 ) After the rotary joint of the swing arm mechanism moves, the hinge point B _i In the lower local coordinate System CoordA _i X _i1 Y _i1 Z _i1 The coordinates of (c) are calculated as:

hinge point C _i CoordB in the upper local coordinate system _i X _i2 Y _i2 Z _i2 Is calculated as:

(4) Coordinate system conversion of hinge point (coordinate calculation of lower hinge point)

Based on hinge point B _i In the lower local coordinate System CoordA _i X _i1 Y _i1 Z _i1 Is (x' _i1’ ，y’ _i1 ，z’ _i1 ) Hinge C _i CoordB in the upper local coordinate system _i X _i2 Y _i2 Z _i2 Is (x' _i2 ，y’ _i2 ，z’ _i2 )；

CoordA in combination with a local coordinate system _i X _i1 Y _i1 Z _i1 Offset from the global coordinate system coordoyx [ delta ] X, [ delta ] Y, [ delta ] Z, [ delta ] α, [ delta ] β, [ delta ] γ [ ]]Then calculate the hinge point C _i In the lower local coordinate System CoordA _i X _i1 Y _i1 Z _i1 Can be expressed as:

then, hinge point C _i The coordinates in the global coordinate system coordoyx are expressed as:

so far, the global coordinate of the lower hinge point coordinate, namely the hinge point C after the swing arm moves _i Coordinates in the global coordinate system coordoyx.

(5) Upper hinge point coordinate calculation

At the initial state, the hinge point D _i The coordinates of the point in the global coordinate system coordoyx are (x) _i3 ，y _i3 ，z _i3 ) The initial length of the electric cylinder is L;

in the first mode, the hinge point D _i X and Y coordinates of (a) 'are constant, X' _i3 ＝x _i3 ，y’ _i3 ＝y _i3 The calculation method of the Z coordinate is as follows;

in the second mode, hinge point D _i The coordinates are unchanged.

Therefore, in the first mode, the moving platform 200 as the upper platform changes the height along with the movement of the swing arm mechanism, but it remains horizontal, the X coordinate and the Y coordinate of the upper hinge point are not changed, and the Z coordinate can be obtained by solving the process of the above embodiment. In the second mode, the coordinates of the upper hinge point of the moving platform 200 are unchanged.

Compared with the prior art, the parallel six-degree-of-freedom motion platform and the motion control method thereof provided by the invention have the advantages that the swing arm mechanism is additionally arranged at the bottom of the electric cylinder of the six-degree-of-freedom motion platform, and the swing arm mechanism is provided with two rotary joints which are respectively driven by the motor and the speed reducer. Through the motion of the swing arm mechanism, the diameter of the hinged circle and the inclination angle of the electric cylinder are changed, so that the rotation rigidity, the transverse translation rigidity and the strokes in all directions of the platform are changed, the structural interference is avoided, and the stability, the reliability, the safety and the application range of the platform motion are improved.

Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the protection scope of the present invention should be determined by the appended claims.

Claims (10)

1. A parallel six-degree-of-freedom motion platform with variable rigidity and stroke is characterized by comprising:

a base (100);

a motion platform (200);

an electric cylinder (400) arranged between the base (100) and the motion platform (200);

the swing arm mechanism is arranged between the base (100) and the motion platform (200), corresponds to each electric cylinder (400) and is positioned below the electric cylinder (400), each swing arm mechanism is arranged on the upper surface of the base (100) and extends towards the motion platform, a lower hook hinge base (300) is arranged at the upper end of the swing arm mechanism, and the bottom of each electric cylinder (400) is supported and hinged to the lower hook hinge base (300) of the corresponding swing arm mechanism;

the upper Hooke joint base (600) is arranged on the lower bottom surface of the motion platform (200), and the upper end and the lower end of each electric cylinder (400) are respectively hinged with the corresponding upper Hooke joint base (600) and the corresponding lower Hooke joint base (300);

the swing arm mechanism corresponding to each electric cylinder (400) is provided with a first rotary joint and a second rotary joint which are respectively positioned at the corresponding positions of an upper Hooke joint base (600) and a lower Hooke joint base (300), and the first rotary joint and the second rotary joint are set to be controlled by consistent synchronous motion so as to enlarge or reduce a lower hinge circle of the parallel type six-freedom-degree motion platform and adjust the rotary rigidity, the transverse translational rigidity and the strokes of the platform in all directions.

2. A parallel six-degree-of-freedom motion platform of variable stiffness and stroke according to claim 1, characterised in that a first ear mount (310) is provided below the lower hooke's joint mount (300);

a second ear seat (110) is arranged on the upper surface of the base (100) corresponding to the lower hook hinge base (300) of each electric cylinder (400); the first ear seat (310) is matched with the second ear seat (110).

3. A parallel six degree of freedom motion platform with variable stiffness and stroke according to claim 2 characterised in that the swing arm mechanism comprises a swing arm (530), the swing arm (530) is provided with a first fork (531) at one end and a second fork (532) at the other end, the first and second rotary joints are provided corresponding to the position of the first and second forks (531, 532), respectively.

4. A parallel six-degree-of-freedom motion platform with variable stiffness and stroke according to claim 3, characterised in that the first rotary joint comprises a first ear mount (310) and a motor drive mechanism arranged coaxially with the first ear mount (310), the first ear mount (310) is mounted in the first fork (531), the output shaft end of the motor drive mechanism passes through the side hole of the first fork (531) and is connected to the rotational centre of the first ear mount (310) by key connection;

the second rotary joint comprises a second ear seat (110) and a motor driving mechanism coaxially arranged with the second ear seat (110), the second ear seat (110) is installed in the second fork part (532), the output shaft end of the motor driving mechanism penetrates through the side hole of the second fork part (532), and the motor driving mechanism is connected to the rotary center of the second ear seat (110) in a key connection mode.

5. A parallel six-degree-of-freedom motion platform with variable stiffness and stroke according to claim 4, wherein the parallel six-degree-of-freedom motion platform with variable stiffness and stroke according to claim 2, wherein the motor driving mechanism comprises a motor and a speed reducing mechanism which are coaxially arranged.

6. A parallel six-degree-of-freedom motion platform with variable stiffness and stroke according to claim 5, characterised in that the speed reduction mechanism is a planetary gear reducer.

7. A parallel six-degree-of-freedom motion platform with variable rigidity and stroke according to claim 1, characterised in that the adjustment of the lower hinge circle of the parallel six-degree-of-freedom motion platform is realized by adjusting the inclination angle of the swing arm mechanism by synchronously controlling the motion of the first rotary joint and the motion of the second rotary joint so that the rotation speed and the rotation angle of the six first rotary joints are consistent and the rotation speed and the rotation angle of the six second rotary joints are consistent.

8. A parallel variable stiffness and stroke six degrees of freedom motion platform according to claim 1 wherein the parallel six degrees of freedom motion platform is configured to operate in at least two modes comprising:

in a first mode: the diameter of the lower hinge circle is changed through the movement of the swing arm mechanism, and the expansion amount of each electric cylinder is unchanged; in the motion driving process, the diameter of the lower hinge circle is enlarged or reduced by driving the six swing arm mechanisms to do consistent synchronous motion;

in a second mode: the motion platform is fixed, and the stretching amount of one or more electric cylinders is changed through the motion of the swing arm mechanism.

9. A motion control method for a parallel six-degree-of-freedom motion platform with variable stiffness and stroke according to any one of claims 1-8, characterized in that the position coordinates of each hinge point in the motion state are calculated by constructing a global coordinate system of an upper plane of a center of a base, a lower local coordinate system of a center of a side hole of an ith second ear seat on the base, and an upper local coordinate system established at a center of a side hole of an ith first ear seat, and by converting and reversely connecting a hinge point coordinate system, the specific implementation process comprises:

setting the central point of the upper plane of the base as O, and constructing a global coordinate system CoordOXYZ of the upper plane of the central plane of the base and a lower local coordinate system CoordA at the center of the side hole of the ith second ear seat of the base _i X _i1 Y _i1 Z _i1 And an upper local coordinate system CoorddB established at the center of the side hole of the ith first ear seat _i X _i2 Y _i2 Z _i2 ；

Solving a hinge point C by acquiring the motion angles of two rotary joints of the swing arm mechanism _i CoordB in the upper local coordinate system _i X _i2 Y _i2 Z _i2 Coordinates of (2), hinge point B _i In the lower local coordinate System CoordA _i X _i1 Y _i1 Z _i1 To obtain the upper local coordinate system CoordB _i X _i2 Y _i2 Z _i2 And the lower local coordinate system CoordA _i X _i1 Y _i1 Z _i1 The conversion relationship of (1);

wherein the hinge point C _i Can be converted into a local coordinate system CoordA through coordinate system conversion _i X _i1 Y _i1 Z _i1 (ii) a Due to the lower local coordinate system CoordA _i X _i1 Y _i1 Z _i1 The transformation relationship with the global coordinate system coordoyx is fixed and known, so the hinge point C is further fixed and known _i The coordinates of the lower hinge point are converted into the coordinates of a global coordinate system CoordOXYZ, namely the global coordinates of the moved lower hinge point are obtained;

and finally, determining the global coordinate of the upper hinge point according to the position change of the motion platform of the parallel six-freedom-degree motion platform in different motion modes.

10. The motion control method of the parallel six-degree-of-freedom motion platform with variable rigidity and stroke according to claim 9, wherein the specific calculation of the global coordinates of the upper hinge point and the lower hinge point comprises:

(1) Definition of coordinate system

Constructing a global coordinate system CoordOXYZ of a plane on the center of the base and a lower local coordinate system Coo at the center of a side hole of the ith second ear seat on the baserdA _i X _i1 Y _i1 Z _i1 And an upper local coordinate system CoordB established at the center of the side hole of the ith first ear seat _i X _i2 Y _i2 Z _i2 ；

(2) Setting initial state of platform

In the initial position, the hinge point C is designed in the design parameters of the platform _i And hinge point D _i Coordinates of the global coordinate system coordoyx, the coordinates of the upper local coordinate system CoordB _i X _i2 Y _i2 Z _i2 Is known; hinge point Bi is in the lower local coordinate system CoordA _i X _i1 Y _i1 Z _i1 Is known;

wherein the hinge point C _i The rotation center point of the bottom of the ith electric cylinder and the corresponding ith lower Hooke hinge base is represented, and a lower hinge point is represented;

hinge point D _i The rotating center point of the top of the ith electric cylinder and the corresponding ith upper hook hinge base is shown, and an upper hinge point is shown;

the hinge point Bi represents a rotation center point of the first fork portion of the swing arm in the swing arm mechanism corresponding to the ith electric cylinder 400 and the corresponding first lug seat; the hinge point Ai represents a rotation central point of the combination of a second fork part of the swing arm in the swing arm mechanism corresponding to the ith electric cylinder and a corresponding second lug seat;

lower local coordinate system CoordA _i X _i1 Y _i1 Z _i1 Offset from the global coordinate system coordoyx [ delta ] X, [ delta ] Y, [ delta ] Z, [ delta ] α, [ delta ] β, [ delta ] γ [ ]]The method comprises the following steps of (1) knowing;

(3) Hinge point coordinate transformation

The second rotary joint and the first rotary joint of the swing arm mechanism respectively surround the Y of the two local coordinate systems _i1 And Y _i2 Rotation, angle of rotation being respectively beta ₁ And beta ₂ ；

At the initial state, the hinge point B _i In the lower local coordinate System CoordA _i X _i1 Y _i1 Z _i1 Has the coordinates of (x) _i1 ，y _i1 ，z _i1 ) Hinge point C _i CoordB in the upper local coordinate system _i X _i2 Y _i2 Z _i2 Has the coordinates of (x) _i2 ，y _i2 ，z _i2 ) After the rotary joint of the swing arm mechanism moves, the hinge point B _i In the lower local coordinate System CoordA _i X _i1 Y _i1 Z _i1 The coordinates of (c) are calculated as:

hinge point C _i CoordB in the upper local coordinate system _i X _i2 Y _i2 Z _i2 The coordinates of (c) are calculated as:

(4) Coordinate system conversion of hinge points

Based on hinge point B _i In the lower local coordinate System CoordA _i X _i1 Y _i1 Z _i1 Is (x' _i1’ ，y’ _i1 ，z’ _i1 ) Hinge C _i CoordB in the upper local coordinate system _i X _i2 Y _i2 Z _i2 Is (x' _i2 ，y’ _i2 ，z’ _i2 )；

CoordA in combination with a local coordinate system _i X _i1 Y _i1 Z _i1 Offset [ DeltaX, deltaY, deltaZ, deltaalpha, deltabeta, deltagamma ] from the global coordinate system CoordOXYZ]Then calculate the hinge point C _i In the lower local coordinate System CoordA _i X _i1 Y _i1 Z _i1 Is expressed as:

then, hinge point C _i The coordinates in the global coordinate system coordoyx are expressed as:

so far, the global coordinate of the lower hinge point coordinate, namely the hinge point C after the swing arm moves _i Coordinates in a global coordinate system coordoyx;

(5) Upper hinge point coordinate calculation

At the initial state, the hinge point D _i The coordinates of the point in the global coordinate system coordoyx are (x) _i3 ，y _i3 ，z _i3 ) The initial length of the electric cylinder is L;

in the first mode, the hinge point D _i X and Y coordinates of (a) 'are constant, X' _i3 ＝x _i3 ，y’ _i3 ＝y _i3 The calculation method of the Z coordinate is as follows;

in the second mode, hinge point D _i The coordinates are unchanged.

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