CN116276907A - Parallel six-degree-of-freedom motion platform with variable rigidity and stroke and motion control method thereof - Google Patents

Abstract

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

Background

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

The parallel six-degree-of-freedom motion platform consists of an upper platform and a lower platform, 6 electric cylinders in the middle and 6 hook joints (or spherical joints) respectively at the upper and lower sides, wherein the lower platform is fixed, the lower platform is connected with the upper platform through the 6 electric cylinders and the hook joints, and the hook joints or the spherical joints are positioned at the connection positions of the upper platform and the 6 electric cylinders, so that the key effect is played on ensuring the normal operation and the whole structural rigidity of the platform. Translation of the upper platform along X, Y, Z and rotational movement about X, Y, Z axis is achieved by telescoping of each motorized cylinder.

The parallel six-degree-of-freedom motion platform is generally driven by a servo electric cylinder, and a hydraulic cylinder is adopted to drive the parallel six-degree-of-freedom motion platform with heavy load. The telescopic movement of the six electric cylinders is controlled to drive the upper platform to move in six degrees of freedom (X, Y, Z, alpha, beta and gamma) in space, so that various spatial movement postures can be simulated, corresponding positions and speed command signals of the electric cylinders are calculated according to the movement states of the six degrees of freedom platform in the movement process, the movement of the movement platform is controlled, movement according to a preset track is ensured, when the movement platform reaches a required position, the speed command signals of the electric cylinders are set to be zero, the movement platform stops, and the purpose of point position control is achieved. Meanwhile, a strategy of closed-loop control is adopted in the motion process, the speed and displacement signals of each electric cylinder are fed back, the speed signals are used for tracking speed input during closed-loop control, and the displacement signals are used for position feedback and monitoring, so that pose control of a motion platform is met.

The parallel six-degree-of-freedom motion platform is driven by 6 servo electric cylinders which are 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. The indexes such as the load capacity, the motion space, the motion speed, the acceleration and the like of the parallel six-degree-of-freedom motion platform are difficult to consider, if the pursuit of the motion space is large, the load capacity needs to be sacrificed, the pursuit of the transverse displacement acceleration is large, and the rotation angular acceleration needs to be sacrificed. Moreover, these performance metrics of the parallel robot are already set after their overall design is determined, which results in a single task for one parallel six-degree-of-freedom motion platform. Under complex working conditions, a parallel six-degree-of-freedom motion platform is difficult to meet the left and right working requirements, the parallel robot is required to have good transverse displacement rigidity or large translation stroke, the parallel robot is required to be designed to be shorter, and the included angle between an electric cylinder and the ground is smaller; the rotation rigidity is good or the rotation angle is large, the rotation angle is required to be designed to be higher, and the included angle between the electric cylinder and the ground is larger. Or to alter the stroke of the electric cylinders to improve these performance indicators. When interference occurs in a certain pose, there is no other method for avoiding the interference besides limiting the travel of the pose.

For example, as shown in fig. 1, the horizontal movement capability and the lateral rigidity of the upper platform are not ideal when the lateral component force is small, and the horizontal movement capability and the lateral rigidity are improved when the lateral component force is increased. With reference to fig. 2, when the transverse component force is small and the α and β moment arms are large, the rotational rigidity is good, but when the transverse component force is increased, the α and β moment arms are reduced, resulting in a problem of reduced rotational ability.

In addition, the problem of structural interference and singular position as shown in fig. 3a and 3b is also a great difficulty in designing and using the six-degree-of-freedom parallel robot, for example, 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 are design defect problems, which can cause serious damage to the electric and moving platforms, which is not allowed, and in the design of the large-tonnage and heavy-load six-degree-of-freedom parallel robot, serious safety accidents can be caused by the structural interference, which is not hopefully and not allowed.

Disclosure of Invention

As a first aspect of the invention, a parallel six-degree-of-freedom motion platform with variable rigidity and stroke is provided, a swing arm mechanism is added at the bottom of an electric cylinder of a six-degree-of-freedom parallel robot, the swing arm mechanism is provided with two rotary joints, the two rotary joints are respectively driven by a motor and a speed reducer, the layout of a lower hinge point is further changed, the diameter of a hinge circle and the inclination angle of the electric cylinder are further changed, the rotation rigidity, the transverse translation rigidity and the stroke of each direction of the platform are further changed, and structural interference is avoided.

As a second aspect of the present invention, a swing arm motion of a parallel six-degree-of-freedom motion platform with variable stiffness and travel is proposed, controlling two modes of operation of the parallel six-degree-of-freedom motion platform:

first mode: the diameter of the lower hinged circle is changed through the movement of the swing arm mechanism, and the expansion and contraction 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;

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

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

As a second aspect of the present invention, a control method of a parallel six-degree-of-freedom motion platform with variable stiffness and stroke is proposed, whose hinge point coordinate calculation method is as follows:

first, a coordinate system is defined: the center point of the plane on the base is set as O, a global coordinate system CoordOXYZ is established on the plane on the center of the base, and a local coordinate system CoordA is established at the center of the ith base connecting ear seat hole _i X _i1 Y _i1 Z _i1 A local coordinate system CoordB is established at the center of the ear seat hole of the ith lower hook joint 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 At the officeCoordB part coordinate system _i X _i2 Y _i2 Z _i2 Coordinates of (c); hinge point B _i In a local coordinate system CoordA _i X _i1 Y _i1 Z _i1 Further, the local coordinate system CoordB can be obtained _i X _i2 Y _i2 Z _i2 With a local coordinate system coorada _i X _i1 Y _i1 Z _i1 Is a conversion relation of (a).

Wherein the hinge point C _i Can be converted into a local coordinate system CoordA by coordinate system conversion _i X _i1 Y _i1 Z _i1 The method comprises the steps of carrying out a first treatment on the surface of the Due to the local coordinate system CoordA _i X _i1 Y _i1 Z _i1 The conversion relation with the global coordinate system CoordOXYZ is fixed and known, so the hinge point C _i Can be further converted into coordinates of a global coordinate system CoordOXYZ.

Therefore, in the first mode, the upper platform can change 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 by solving. In the second mode, the upper platform hinge point coordinates 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 added 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 driven by a motor and a speed reducer respectively. Through the movement 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 travel in all directions of the platform are changed, structural interference is avoided, and the stability, the reliability, the safety and the application range of the movement of the platform are improved.

It should be understood that all combinations of the foregoing concepts, as well as additional concepts described in more detail below, may be considered a part of the inventive subject matter of the present disclosure as long as such concepts are not mutually inconsistent. In addition, all combinations of claimed subject matter are considered part of the disclosed inventive subject matter.

The foregoing and other aspects, embodiments, and features of the present teachings will be more fully understood from the following description, taken together with the accompanying drawings. Other additional aspects of the invention, such as features and/or advantages of the exemplary embodiments, will be apparent from the description which follows, or may be learned by practice of the embodiments according to the teachings of the invention.

Drawings

The drawings 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 invention will now be described, by way of example, with reference to the accompanying drawings, in which:

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

Fig. 2 is a schematic diagram of a platform before and after adjustment of the α, β -direction rotation arms in the prior art.

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

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

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

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

Fig. 7 is an isometric view of the initial position of the parallel six-degree-of-freedom motion stage of the embodiment of fig. 4.

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

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

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

FIG. 11 is an isometric view of a parallel six-degree-of-freedom motion platform in a contracted state of the articulated circle in the example of FIG. 10.

Detailed Description

For a better understanding of the technical content of the present invention, specific examples are set forth below, along with the accompanying drawings.

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

As shown in connection with fig. 4 to 6, the parallel six-degree-of-freedom motion platform according to the disclosed embodiment of the present invention 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 driving the multi-degree-of-freedom posture adjustment of the motion platform 200 by controlling the telescopic motion of the electric cylinder 400, so as to realize multi-degree-of-freedom motion simulation.

The parallel six-degree-of-freedom motion platform shown in fig. 4 further includes an upper hook base 600 disposed on the lower bottom surface of the motion platform 200, and correspondingly, each upper hook base 600 is provided with a lower hook base 300, and the lower hook bases 300 are correspondingly supported on the upper ends of the swing arm mechanisms, and the lower ends of the swing arm mechanisms are supported on the upper surface of the base 100.

Referring to fig. 4, 5 and 6, six electric cylinders 400 are respectively configured with their corresponding upper hook bases 600, lower hook bases 300 and swing arm mechanisms, and the upper and lower ends of each electric cylinder 400 are hinged between the corresponding upper hook bases 600, lower hook bases 300.

In connection with the example shown in fig. 4 and 5, a first ear mount 310 is provided below the lower hook hinge mount 300. Accordingly, the upper surface of the base 100 is provided with a second ear mount 110 corresponding to the lower hook mount 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, and is used for expanding or contracting the lower hinge circle, so as to change the rotation rigidity, the transverse translational rigidity and the travel in all directions of the platform, and avoid structural interference.

The lower hinge circle refers to a hinge circle formed by a hinge point at the lower end of an electric cylinder, and in the traditional platform design with a fixed position, the diameter and the position of the lower hinge circle are determined by a hinge hook hinge arranged on the lower platform and are fixed, so that the lower hinge circle has the problems of rotation rigidity, transverse translational rigidity and strokes in all directions under complex working conditions as described in the background of the invention.

In an alternative embodiment, each swing arm mechanism is configured with two rotary joints, namely a first rotary joint (an upper rotary joint) correspondingly arranged at the first ear seat 310 and a second rotary joint (a lower rotary joint) arranged at the second ear seat 110, and 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 strokes of all directions of the platform are changed, and structural interference is avoided.

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

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

The second ear mount 110 is mounted inside 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 coaxially arranged with the corresponding first ear mount 310 or second ear mount 110. In an alternative embodiment, each speed reducer output is connected to a corresponding ear mount via a key connection.

Specifically, the motor driving mechanism disposed at the position of the first ear mount 310 includes a first motor 511 and a first speed reducer 512, the first motor 511 employs a stepping motor, an output shaft of which is connected to an input end of the first speed reducer 512, the first speed reducer 512 preferably employs a planetary gear reduction mechanism, and an output end of which is keyed to a rotation center of the first ear mount 310 to drive rotation, thereby adjusting rotation of the first rotary joint.

In an alternative embodiment, the output shaft end of the first speed 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 respectively composed of corresponding ear seats and motor driving mechanisms, and are matched with corresponding fork parts (531, 532) to realize rotary driving of the joints.

As shown in fig. 4 and 5, the motor driving mechanism disposed at the position of the second ear mount 110 includes a second motor 521 and a first speed reducer 522, the second motor 521 may be a stepping motor, an output shaft of which is connected to an input end of the second speed reducer 522, and the second speed reducer 522 preferably employs a planetary gear reduction mechanism, an output end of which is keyed to a rotation center of the second ear mount 110 to drive rotation, thereby adjusting rotation of the second rotary joint.

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

In the design of two rotary joints, as shown in fig. 4 and 5, 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 with the rotation center position of the corresponding ear seat.

It should be appreciated that under the teachings of the present invention, the rotational drive mechanism for both rotational joints can be implemented using existing high integration drive mechanisms to achieve rotational drive designs for joint positions.

Therefore, as shown in fig. 5 and 6, for the swing arm mechanism corresponding to the six electric cylinders arranged on the platform, through synchronously driving the first rotary joint and the second rotary joint, the first rotary joint is kept to move in the same way, the second rotary joint is kept to move in the same way, so that the diameter of the lower hinge circle is changed, the expansion and contraction amount of the electric cylinders is unchanged, the diameter of the lower hinge circle is enlarged, expanded and contracted, the adjustment of the rotation rigidity, the transverse translation rigidity and the stroke in all directions is realized, and the device is suitable for application under complex working conditions, and particularly in the case of large stroke in the horizontal transverse movement direction, the contradiction between the rotation rigidity and the rotation angle is balanced.

As shown in fig. 8-9, which schematically illustrate the enlarged 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 rotary joints and the motion of the second rotary joints, the rotation speeds and rotation angles of the 6 first rotary joints are identical, and the rotation speeds and rotation angles of the 6 second rotary joints are identical, the inclination angle of the swing arm 530, that is, the inclination angle of the swing arm mechanism is adjusted, and the expansion is performed in the edge direction of the base 110, so that the adjustment of the inclination angle of the electric cylinder 400 is realized, and the lower hinge circle is enlarged.

As shown in fig. 10-11, which schematically illustrate a reduced 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 rotary joints and the motion of the second rotary joints, the rotation speeds and rotation angles of the 6 first rotary joints are identical, and the rotation speeds and rotation angles of the 6 second rotary joints are identical, the tilt angle of the swing arm 530 is adjusted, and the swing arm is contracted toward the center origin direction of the base 110, so that the adjustment of the tilt angle of the electric cylinder 400 is realized, and the lower hinge circle is reduced.

Based on the parallel six-degree-of-freedom motion platform with variable stiffness and stroke and the motion control process thereof in combination with the example shown in fig. 4 and fig. 7-11, the parallel six-degree-of-freedom motion platform of the present invention can be set into two working modes:

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

second mode: the upper platform and the lower platform moving platform are kept fixed, and the expansion and contraction 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, through practical processes and tests of the design and the used multi-degree-of-freedom platform, it is found that, as the electric cylinder is usually determined according to design parameters, the larger the dimension difference between an upper hinge circle and a lower hinge 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, and the larger the size difference between the upper hinge circle and the lower hinge circle of the parallel six-degree-of-freedom motion platform is, the larger the inclination angle of the electric cylinder is, the larger the translation stroke is, and the smaller the rotation stroke is.

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

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

As the second aspect of the invention, a control method of a parallel six-degree-of-freedom motion platform with variable rigidity and travel is provided by constructing a global coordinate system CoordOXYZ of a plane on the center of a base and a lower local coordinate system CoordA of the center of a side hole of an ith second ear seat on the base _i X _i1 Y _i1 Z _i1 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 inverse connection of the coordinate system of the hinge point.

As an alternative embodiment, the position coordinates of each hinge point in the motion state are calculated through conversion and inverse connection of the coordinate system of the hinge point, and the process includes:

first, a coordinate system is defined: establishing a global coordinate system CoordOXYZ of the upper plane of the center of the base and a lower local coordinate system CoordA of the center of the side hole of the ith second ear seat on the base by taking the center point of the upper plane of the base as O _i X _i1 Y _i1 Z _i1 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 ；

Solving the hinging point C by acquiring the motion angles of two rotary joints of the swing arm mechanism _i CoordB in upper local coordinate system _i X _i2 Y _i2 Z _i2 Is the coordinate of the 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 With the lower local coordinate system coorada _i X _i1 Y _i1 Z _i1 Is a conversion relation of (a).

Wherein the hinge point C _i Can be converted into a lower local coordinate system CoordA by coordinate system conversion _i X _i1 Y _i1 Z _i1 The method comprises the steps of carrying out a first treatment on the surface of the Due to the lower local coordinate system CoordA _i X _i1 Y _i1 Z _i1 The conversion relation with the global coordinate system CoordOXYZ is fixed and known, so the hinge can be usedContact C _i Can be further converted into coordinates of a global coordinate system CoordOXYZ.

(1) Coordinate system definition

Constructing a global coordinate system CoordOXYZ of a plane on the center of the base and a lower local coordinate system CoordA of the center of a side hole of an ith second ear seat on the base _i X _i1 Y _i1 Z _i1 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 the initial state of the platform

In connection with fig. 4, 6 and 7, at the initial position state, the hinge point C is among the design parameters of the platform _i And hinge point D _i The coordinates of the global coordinate system CoordOXYZ of (C) are known, and the upper local coordinate system CoordB is known _i X _i2 Y _i2 Z _i2 Is known; hinge point Bi 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 i-th electric cylinder 400 and the corresponding i-th lower hook hinge base 300 is shown, and the lower hinge point is shown.

Hinge point D _i Indicating the rotation center point of the top of the i-th electric cylinder 400 and the corresponding i-th upper hook hinge base 600, indicating the upper hinge point.

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 i-th electric cylinder 400.

The hinge point Ai represents the rotation center point of the second fork 532 of the swing arm and the corresponding second ear mount 110 in the swing arm mechanism corresponding to the i-th electric cylinder 400. 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 coorada _i X _i1 Y _i1 Z _i1 Offset from global coordinate system CoordOXYZ [. DELTA.X, DELTA.Y, DELTA.Z, DELTA.alpha, DELTA.beta, DELTA.gamma]Is known.

(3) Hinge point coordinate conversion

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

In the initial state, the 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 point C _i CoordB in upper local coordinate system _i X _i2 Y _i2 Z _i2 Is (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 (a) are calculated as:

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

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

Based on the 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 upper local coordinate system _i X _i2 Y _i2 Z _i2 Is (x' _i2 ，y’ _i2 ，z’ _i2 )；

Combined with a local coordinate system coorada _i X _i1 Y _i1 Z _i1 Offset from global coordinate system CoordOXYZ[△X，△Y，△Z，△α，△β，△γ]Then calculate the hinge point C _i In the lower local coordinate system CoordA _i X _i1 Y _i1 Z _i1 The coordinates of (c) can be expressed as:

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

so far, the global coordinate of the lower hinge point coordinate, namely the hinge point C after the swing arm moves is obtained _i In the global coordinate system CoordOXYZ.

(5) Upper hinge point coordinate calculation

In the initial state, the hinge point D _i The point has a coordinate (x) in the global coordinate system CoordOXYZ _i3 ，y _i3 ，z _i3 ) The initial length of the electric cylinder is L;

in the first mode, the hinge point D _i Is unchanged from the X-coordinate and Y-coordinate of (2), 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.

Thus, in the first mode, the moving platform 200 as the upper platform changes its height with the movement of the swing arm mechanism, but it remains horizontal, and the X-coordinate and the Y-coordinate of the upper hinge point are unchanged, and the Z-coordinate can be obtained by solving the procedure of the above embodiment. In the second mode, the upper hinge point coordinates of motion 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 added 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 driven by a motor and a speed reducer respectively. Through the movement 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 travel in all directions of the platform are changed, structural interference is avoided, and the stability, the reliability, the safety and the application range of the movement of the platform are improved.

While the invention has been described with reference to preferred embodiments, it is not intended to be limiting. Those skilled in the art will appreciate that various modifications and adaptations can be made without departing from the spirit and scope of the present invention. Accordingly, the scope of the invention is defined by the appended claims.

Claims (10)

1. A parallel six-degree-of-freedom motion platform with variable stiffness and travel, comprising:

a base (100);

a motion platform (200);

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

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

the upper Hooke's hinge 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's hinge base (600) and lower Hooke's hinge 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 positions corresponding to the upper hook hinge base (600) and the lower hook hinge base (300), and the first rotary joint and the second rotary joint are controlled through uniform synchronous motion so as to expand or reduce the lower hinge circle of the parallel six-degree-of-freedom motion platform, so that the rotation rigidity, the transverse translation rigidity and the travel of each direction of the platform are adjusted.

2. The parallel six-degree-of-freedom motion platform of variable stiffness and travel of claim 1 wherein a first ear mount (310) is provided below the lower hook mount (300);

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

3. The six degree of freedom motion platform of claim 2 wherein the swing arm mechanism includes a swing arm (530), the swing arm (530) being provided with a first fork (531) at one end and a second fork (532) at the other end, the first and second rotary joints being provided in correspondence with the positions of the first and second forks (531, 532), respectively.

4. A six degrees of freedom motion platform with variable stiffness and stroke according to claim 3, characterized in that the first rotary joint comprises a first ear mount (310) and a motor driving mechanism coaxially arranged with the first ear mount (310), the first ear mount (310) being mounted in a first fork (531), an output shaft end of the motor driving mechanism passing through a side hole of the first fork (531) and being connected to a rotation center position of the first ear mount (310) by means of a 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 arranged in a second fork part (532), and the output shaft end of the motor driving mechanism penetrates through a side hole of the second fork part (532) and is connected to the rotation center position of the second ear seat (110) in a key connection mode.

5. The variable stiffness and stroke parallel six degree of freedom motion platform of claim 4 wherein the variable stiffness and stroke parallel six degree of freedom motion platform of claim 2 wherein the motor drive mechanism comprises a coaxially disposed motor and reduction mechanism.

6. The variable stiffness and stroke parallel six degrees of freedom motion platform of claim 5 wherein the reduction mechanism is a planetary gear reducer.

7. The six-degree-of-freedom motion platform with variable rigidity and stroke according to claim 1, wherein the adjustment of the lower hinge circle of the six-degree-of-freedom motion platform with the parallel type is achieved by synchronously controlling the movement of the first rotary joints and the movement of the second rotary joints so that the rotation speeds and the rotation angles of the six first rotary joints are identical and the rotation speeds and the rotation angles of the six second rotary joints are identical.

8. The variable stiffness and stroke parallel six degree of freedom motion platform of claim 1 configured to operate in at least two modes, comprising:

first mode: the diameter of the lower articulated circle is changed through the movement of the swing arm mechanism, and the expansion and contraction amount of each electric cylinder is unchanged; in the motion driving process, six swing arm mechanisms are driven to make uniform synchronous motion, so that the diameter of the lower hinge circle is enlarged or reduced;

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

9. The motion control method of a parallel six-degree-of-freedom motion platform with variable stiffness and stroke according to any one of claims 1 to 8, wherein 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 side hole center of an i-th second ear seat on the base, and an upper local coordinate system established at a side hole center of an i-th first ear seat through conversion and inverse connection of the hinge point coordinate systems, and the specific implementation process comprises:

establishing a global coordinate system CoordOXYZ of the upper plane of the center of the base and a lower local coordinate system CoordA of the center of the side hole of the ith second ear seat on the base by taking the center point of the upper plane of the base as O _i X _i1 Y _i1 Z _i1 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 ；

Solving the hinging point C by acquiring the motion angles of two rotary joints of the swing arm mechanism _i CoordB in upper local coordinate system _i X _i2 Y _i2 Z _i2 Is the coordinate of the 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 With the lower local coordinate system coorada _i X _i1 Y _i1 Z _i1 Is a conversion relation of (a);

wherein the hinge point C _i Can be converted into a lower local coordinate system CoordA by coordinate system conversion _i X _i1 Y _i1 Z _i1 The method comprises the steps of carrying out a first treatment on the surface of the Due to the lower local coordinate system CoordA _i X _i1 Y _i1 Z _i1 The conversion relation with the global coordinate system CoordOXYZ is fixed and known, so the hinge point C is further defined _i The coordinates of the lower hinge point after the movement are converted into the coordinates of a global coordinate system CoordOXYZ, namely the global coordinates of the lower hinge point after the movement are obtained;

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

10. The method for motion control of a six degrees of freedom motion platform with variable stiffness and stroke according to claim 9, wherein the specific calculation of global coordinates of the upper and lower hinge points comprises:

(1) Coordinate system definition

Constructing a global coordinate system CoordOXYZ of a plane on the center of the base and a lower local coordinate system CoordA of the center of a side hole of an ith second ear seat on the base _i X _i1 Y _i1 Z _i1 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 the initial state of the platform

In the initial position state, the hinge point C is among the design parameters of the platform _i And hinge point D _i The coordinates of the global coordinate system CoordOXYZ of (C) are known, and the upper local coordinate system CoordB is known _i X _i2 Y _i2 Z _i2 Is known; hinge point Bi in the lower local coordinate system CoordA _i X _i1 Y _i1 Z _i1 Is known;

wherein the hinge point C _i Representing the rotation center point of the bottom of the ith electric cylinder and the corresponding ith lower hook hinge base, and representing a lower hinge point;

hinge point D _i Representing the rotation center point of the top of the ith electric cylinder and the corresponding ith upper hook hinge base, and representing an upper hinge point;

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

lower local coordinate system coorada _i X _i1 Y _i1 Z _i1 Offset from global coordinate system CoordOXYZ [. DELTA.X, DELTA.Y, DELTA.Z, DELTA.alpha, DELTA.beta, DELTA.gamma]Is known;

(3) Hinge point coordinate conversion

The second rotary joint and the first rotary joint of the swing arm mechanism respectively wind Y of two local coordinate systems _i1 And Y _i2 Rotating with the rotation angles beta respectively ₁ And beta ₂ ；

In the initial state, the 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 point C _i CoordB in upper local coordinate system _i X _i2 Y _i2 Z _i2 Is (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 (a) are calculated as:

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

(4) Coordinate system conversion of hinge points

Based on the 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 upper local coordinate system _i X _i2 Y _i2 Z _i2 Is (x' _i2 ，y’ _i2 ，z’ _i2 )；

Combined with a local coordinate system coorada _i X _i1 Y _i1 Z _i1 Offset from global coordinate system CoordOXYZ [. DELTA.X, DELTA.Y, DELTA.Z, DELTA.alpha, DELTA.beta, DELTA.gamma]Then calculate the hinge point C _i In the lower local coordinate system CoordA _i X _i1 Y _i1 Z _i1 The coordinates of (c) are expressed as:

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

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

(5) Upper hinge point coordinate calculation

In the initial state, the hinge point D _i The point has a coordinate (x) in the global coordinate system CoordOXYZ _i3 ，y _i3 ，z _i3 ) The initial length of the electric cylinder is L;

in the first mode, the hinge point D _i Is unchanged from the X-coordinate and Y-coordinate of (2), 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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