Parallel mechanism capable of switching working modes for motion simulator and construction method of parallel mechanism

Abstract

The invention belongs to the technical field of parallel mechanisms, and provides a parallel mechanism capable of switching working modes for a motion simulator and a construction method thereof.The parallel mechanism comprises a movable platform, a fixed platform, a first UPU branch chain, a first RPU branch chain and a second RPU branch chain, the first UPU branch chain, the first RPU branch chain and the second RPU branch chain are arranged between the movable platform and the fixed platform, and the three branch chains are arranged at the corner edges of the fixed platform correspondingly; the mechanism is of a 2-RPU-UPU configuration, when the movable platform and the fixed platform are parallel, and the center points of the movable platform and the fixed platform are vertically collinear, a 2T1R mode and a 2R1T mode are switched, and the working modes are switched through four driving pair control mechanisms in the initial configuration. And the movable platform is driven to realize movement and mutual switching of a 2T1R mode and a 2R1T mode relative to the fixed platform so as to adapt to different working environments to switch the working modes, and the mechanism has the advantages of strong adaptability, high rigidity, strong bearing capacity, good dynamic performance and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of parallel mechanisms, and in particular relates to a parallel mechanism capable of switching working modes for a motion simulator and a construction method thereof. Background Art

[0002] Motion simulator is a mechanical device used to simulate the real movement of objects. It has the advantages of safety, high efficiency, economy, and no influence from external environmental factors. It is mainly used in the fields of simulated flight of aircraft, simulated navigation of ships, driving test of cars, simulation test of tanks, and entertainment facilities. Motion simulator plays a vital role in the development of national military and civil affairs. It provides experience for operators in actual operation and improves the efficiency of training. The research of motion simulator is particularly critical.

[0003] Although the current motion simulators have their own advantages and have achieved good simulation effects and improved training efficiency in many fields, they also have some shortcomings. Most motion simulators have a large number of kinematic pairs, which increases the manufacturing cost of the motion simulators; some motion simulators, although the production cost is not high, cannot withstand large loads and can only be used for small load movements; most existing simulators simulate a single motion mode and cannot be used to simulate multiple working modes. They are complex and inflexible, the mode switching process is complicated, and the working modes are prone to interfere with each other. Therefore, it is necessary to propose a parallel mechanism for a motion simulator that can switch working modes and a construction method thereof. Summary of the invention

[0004] In view of the problems existing in the prior art, the present invention provides a parallel mechanism for a motion simulator capable of switching working modes and a construction method thereof. The working mode can be switched by moving the four driving sub-control mechanisms in the initial configuration. By controlling the three moving sub-control mechanisms in each branch chain and the first universal joint outer rotating sub-control mechanism of the first UPU branch chain, the moving platform is driven relative to the fixed platform to realize the movement and mutual switching between the 2T1R mode and the 2R1T mode, so as to switch the working mode to adapt to different working environments. The invention has the advantages of strong adaptability, high rigidity, strong bearing capacity and good dynamic performance. The invention solves the problem that the existing parallel mechanism has a single structure and cannot meet the working requirements under complex conditions.

[0005] The present invention provides a parallel mechanism for a motion simulator capable of switching working modes, which comprises a moving platform, a fixed platform, and a first UPU branch chain, a first RPU branch chain, and a second RPU branch chain arranged between the moving platform and the fixed platform. The moving platform and the fixed platform are both triangular structures. The first UPU branch chain, the first RPU branch chain, and the second RPU branch chain are respectively arranged at the edges of the corner vertices of the fixed platform. The outer rotating shaft of the second universal joint in the first UPU branch chain, the first rotating pair in the first RPU branch chain, and the second rotating pair in the second RPU branch chain are fixedly connected to the fixed platform. The first UPU branch chain is connected to the fixed platform. The outer rotating shaft of the universal joint, the third universal joint in the first RPU branch chain, and the fourth universal joint in the second RPU branch chain are fixedly connected to the moving platform; the first UPU branch chain includes a first universal joint, a first movable pair, and a second universal joint, the inner rotating shaft of the second universal joint is connected to the inner rotating shaft of the first universal joint through the first movable pair, and the inner rotating axis of the second universal joint is parallel to the inner rotating axis of the first universal joint; the first RPU branch chain and the second RPU branch chain have the same structure, the first RPU branch chain includes a first rotating pair, a second movable pair, and a third universal joint, the inner rotating shaft of the first rotating pair is connected to the first movable pair, and the inner rotating axis of the second universal joint is parallel to the inner rotating axis of the first universal joint. The inner rotating shafts of the three universal joints are connected through the second movable pair, and the inner rotating shaft of the first rotating pair is parallel to the inner rotating axis of the third universal joint; the second RPU branch chain includes a second rotating pair, a third movable pair and a fourth universal joint, the inner rotating shaft of the second rotating pair is connected to the inner rotating shaft of the fourth universal joint through the third movable pair, and the inner rotating axis of the second rotating pair is parallel to the inner rotating axis of the fourth universal joint; the outer rotating axis of the first universal joint in the first UPU branch chain, the first rotating pair axis in the first RPU branch chain and the second rotating pair axis in the second RPU branch chain are parallel to each other, the first universal joint, The third universal joint and the fourth universal joint are respectively arranged at the corner edges of the moving platform, and the axis of the outer rotating shaft of the third universal joint is colinear with the axis of the outer rotating shaft of the fourth universal joint, and the outer rotating axis of the first universal joint is perpendicular to the outer rotating axis of the third universal joint; the first moving pair in the first UPU branch, the second moving pair in the first RPU branch, the third moving pair in the second RPU branch and the first universal joint outer rotating shaft of the first UPU branch serve as driving pairs, and the four driving pairs drive the moving platform relative to the fixed platform to realize the movement and mutual switching of the spatial 2T1R working mode and 2R1T working mode.

[0006] Preferably, the mechanism is of 2-RPU-UPU configuration, and when the moving platform is parallel to the fixed platform and the center points of the two are vertically collinear, the 2T1R working mode and the 2R1T working mode can be switched, and there is no need to reorganize the mechanism when switching the working mode, and the working mode can be switched only by moving the initial position control mechanism.

[0007] Preferably, the center of the fixed platform is the coordinate origin, the direction parallel to the first rotating secondary axis in the first RPU branch chain is the x-axis, the direction parallel to the outer rotating axis axis of the third universal joint in the first RPU branch chain is the y-axis, and the direction perpendicular to the fixed platform is the z-axis.

[0008] Preferably, the mechanism has 2R2T motion in the initial position, namely movement along the z-axis, movement along the y-axis, rotation around the y-axis and rotation around the x-axis. The first moving pair in the first UPU branch, the second moving pair in the first RPU branch, the third moving pair in the second RPU branch and the outer rotating shaft of the first universal joint of the first UPU branch serve as driving pairs. When the mechanism rotates around the y-axis, it will lose the ability to move along the y-axis, and after rotating around the y-axis, it will lose the ability to move along the y-axis direction.

[0009] Preferably, the first moving pair, the second moving pair and the third moving pair are all composed of a sliding rod and a sliding sleeve.

[0010] Preferably, the first universal joint, the second universal joint, the third universal joint and the fourth universal joint are each composed of two mutually perpendicular rotation axes.

[0011] In a second aspect, the present invention provides a method for constructing a parallel mechanism capable of switching working modes for a motion simulator, comprising the following steps:

[0012] S1. Based on the finite screw method, the finite motion and instantaneous motion of the existing variable degree of freedom branch chain are analyzed, and the variable degree of freedom generators are decomposed;

[0013] S2. Determine the expected motion of the multi-mode parallel mechanism according to the requirements of the motion simulator. f,PM}, and the fixed degree of freedom branch chain output motion {S f,IVM} standard type and variable degree of freedom branch chain output motion {S f,VM}Standard type;

[0014] S3. Based on the screw trigonometric product operation rule, the fixed-degree-of-freedom derivative formula is derived according to the fixed-degree-of-freedom standard form, and then the fixed-degree-of-freedom branched chain configuration is obtained;

[0015]

[0016] Where θ is the rotation angle of the rigid body around the Chasles axis relative to the reference position, τ is the translation distance along the Chasles axis, s is the direction unit vector of the axis, and r is the position vector of the axis.

[0017]

[0018] S4. Based on the screw trigonometric product operation rule, the variable degree of freedom derivative formula is derived according to the variable degree of freedom standard form, and the variable degree of freedom generator is selected to add to the branch chain. On this basis, the remaining kinematic pairs are integrated to obtain the variable degree of freedom branch chain configuration;

[0019] S5. Based on the assembly conditions of the multi-mode parallel mechanism, the fixed degree of freedom branch configuration and the variable degree of freedom branch configuration, a parallel mechanism that can switch working modes is constructed.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] The present invention is a parallel mechanism for a motion simulator capable of switching working modes. By controlling four driving pairs in each branch chain, the dynamic platform is driven relative to the fixed platform to realize the movement and mutual switching between the 2T1R mode and the 2R1T mode, so as to switch the working mode to adapt to different working environments. The present invention has the advantages of strong adaptability, high rigidity, strong bearing capacity and good dynamic performance. Based on the finite screw method, an analysis and classification method of variable degree of freedom generators is proposed, and a new method for synthesizing the configuration of a multi-mode parallel mechanism based on variable degree of freedom branches is used to solve the problem that the existing parallel mechanism has a single structure and cannot meet the working requirements under complex circumstances. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is an overall structural diagram of the parallel mechanism capable of switching working modes used in the motion simulator of the present invention;

[0023] Figure 2 It is a schematic diagram of the initial state of the parallel mechanism capable of switching working modes of the present invention;

[0024] Figure 3 It is a schematic diagram of the structure of the first UPU branch in the present invention;

[0025] Figure 4 It is a schematic diagram of the structure of the first RPU branch in the present invention;

[0026] Figure 5 Schematic diagram of the structure of the second RPU branch in the present invention;

[0027] Figure 6 This is a schematic diagram of the structure of the connection between the moving platform and each branch chain of the present invention;

[0028] Figure 7 This is a schematic diagram of the structure of the connection between the fixed platform and each branch chain of the present invention;

[0029] Figure 8 The present invention is a flow chart of a construction method of a parallel mechanism capable of switching working modes.

[0030] Main drawings marked:

[0031] The first UPU branch chain 1, the first universal joint U1, the first movable pair P1, the second universal joint U2, the first RPU branch chain 2, the first rotating pair R1, the second movable pair P2, the third universal joint U3, the second RPU branch chain 3, the second rotating pair R2, the third movable pair P3, the fourth universal joint U4, the fixed platform 4, and the movable platform 5. DETAILED DESCRIPTION

[0032] In order to fully describe the technical content, structural features, objectives and effects of the present invention, the following will be described in detail with reference to the accompanying drawings.

[0033] The present invention is used for a parallel mechanism of a motion simulator capable of switching working modes, such as Figure 1 and Figure 2 As shown, it includes a moving platform 5, a fixed platform 4, and a first UPU branch 1, a first RPU branch 2, and a second RPU branch 3 arranged between the moving platform 5 and the fixed platform 4. The moving platform 5 and the fixed platform 4 are both triangular structures. The first UPU branch 1, the first RPU branch 2, and the second RPU branch 3 are respectively arranged at the edges of the corner vertices of the fixed platform 4. The first moving pair P1 in the first UPU branch 1, the second moving pair P2 in the first RPU branch 2, the third moving pair P3 in the second RPU branch 3, and the outer rotating shaft of the first universal joint U1 of the first UPU branch 1 serve as driving pairs. The four driving pairs drive the moving platform 5 relative to the fixed platform 4 to realize the movement and mutual switching of the spatial 2T1R working mode and the 2R1T working mode.

[0034] like Figure 3 As shown, the first UPU branch chain 1 includes a first universal joint U1, a first movable pair P1 and a second universal joint U2. The inner rotating shaft of the second universal joint U2 is connected to the inner rotating shaft of the first universal joint U1 through the first movable pair P1, and the inner rotating axis of the second universal joint U2 is parallel to the inner rotating axis of the first universal joint U1.

[0035] like Figure 4 and Figure 5 As shown, the first RPU branch 2 and the second RPU branch 3 have the same structure. The first RPU branch 2 includes a first rotating pair R1, a second movable pair P2 and a third universal joint U3. The inner rotating shaft of the first rotating pair R1 is connected to the inner rotating shaft of the third universal joint U3 through the second movable pair P2, and the inner rotating shaft of the first rotating pair R1 is parallel to the inner rotating axis of the third universal joint U3; the second RPU branch 3 includes a second rotating pair R2, a third movable pair P3 and a fourth universal joint U4. The inner rotating shaft of the second rotating pair R2 is connected to the inner rotating shaft of the fourth universal joint U4 through the third movable pair P3, and the inner rotating axis of the second rotating pair R2 is parallel to the inner rotating axis of the fourth universal joint U4.

[0036] like Figure 6 and Figure 7As shown, the outer rotating shaft of the second universal joint U2 in the first UPU branch chain 1, the first rotating pair R1 in the first RPU branch chain 2, and the second rotating pair R2 in the second RPU branch chain 3 are fixedly connected to the fixed platform 4, and the outer rotating shaft of the first universal joint U1 in the first UPU branch chain 1, the third universal joint U3 in the first RPU branch chain 2, and the fourth universal joint U4 in the second RPU branch chain 3 are fixedly connected to the moving platform 5. The outer rotating axis of the first universal joint U1 in the first UPU branch chain 1, the axis of the first rotating pair R1 in the first RPU branch chain 2, and the axis of the second rotating pair R2 in the second RPU branch chain 3 are parallel to each other, the first universal joint U1, the third universal joint U3, and the fourth universal joint U4 are respectively arranged at the corner edges of the moving platform 5, and the axis of the outer rotating shaft of the third universal joint U3 is colinear with the axis of the outer rotating shaft of the fourth universal joint U4, and the outer rotating axis of the first universal joint U1 is perpendicular to the outer rotating axis of the third universal joint U3. The first moving pair P1, the second moving pair P2 and the third moving pair P3 are all composed of a sliding rod and a sliding sleeve. The first universal joint U1, the second universal joint U2, the third universal joint U3 and the fourth universal joint U4 are all composed of two mutually perpendicular rotation axes.

[0037] The parallel mechanism used for the motion simulator to switch working modes is a 2-RPU-UPU configuration. When the moving platform 5 is parallel to the fixed platform 4 and the center points of the two are vertically collinear, the 2T1R working mode and the 2R1T working mode can be switched. There is no need to reorganize the mechanism when switching the working mode. The working mode can be switched by controlling the movement of the mechanism only in the initial configuration. The center of the fixed platform 4 is taken as the coordinate origin, the direction parallel to the axis of the first rotating pair R1 in the first RPU branch chain 2 is taken as the x-axis, the direction parallel to the axis of the outer rotating shaft of the third universal joint U3 in the first RPU branch chain 2 is taken as the y-axis, and the direction perpendicular to the fixed platform 4 is taken as the z-axis. The mechanism has 2R2T motion in the initial position, namely movement along the z-axis, movement along the y-axis, rotation around the y-axis and rotation around the x-axis. The first moving pair P1 in the first UPU branch 1, the second moving pair P2 in the first RPU branch 2, the third moving pair P3 in the second RPU branch 3 and the outer rotating shaft of the first universal joint U1 of the first UPU branch 1 serve as driving pairs. When the mechanism rotates around the y-axis, it will lose the ability to move along the y-axis, and after rotating around the y-axis, it will lose the ability to move along the y-axis direction.

[0038] like Figure 8 As shown, a method for constructing a parallel mechanism capable of switching working modes for a motion simulator comprises the following steps:

[0039] S1. Based on the finite screw method, the finite motion and instantaneous motion of the existing variable degree of freedom branch are analyzed, and the variable degree of freedom generators are decomposed.

[0040] S2. Determine the expected motion of the multi-mode parallel mechanism according to the requirements of the motion simulator. f,PM}, and the fixed degree of freedom branch chain output motion {S f,IVM} standard type and variable degree of freedom branch chain output motion {S f,VM} standard type.

[0041] S3. Based on the spinor trigonometric product operation rules, the fixed-degree-of-freedom derivative formula is derived according to the fixed-degree-of-freedom standard form, and then the fixed-degree-of-freedom branched chain configuration is obtained.

[0042]

[0043] Where θ is the rotation angle of the rigid body around the Chasles axis relative to the reference position, τ is the translation distance along the Chasles axis, s is the direction unit vector of the axis, and r is the position vector of the axis.

[0044]

[0045] S4. Based on the spinor trigonometric product operation rules, the variable degree of freedom derivative formula is derived according to the variable degree of freedom standard form, the variable degree of freedom generator is selected to add to the branch chain, and the remaining kinematic pairs are integrated on this basis to obtain the variable degree of freedom branch chain configuration.

[0046] S5. Based on the assembly conditions of the multi-mode parallel mechanism, the fixed degree of freedom branch configuration and the variable degree of freedom branch configuration, a parallel mechanism that can switch working modes is constructed.

[0047] The following is a further description of the method for constructing a parallel mechanism capable of switching working modes for a motion simulator according to the present invention in combination with an embodiment:

[0048] The present invention provides a method for constructing a parallel mechanism capable of switching working modes for a motion simulator, and for a parallel mechanism having a 2T1R working mode and a 2R1T working mode, the method comprises the following steps:

[0049] S1. Based on the finite screw method, the finite motion and instantaneous motion of the existing variable degree of freedom branch chain are analyzed, the kinematic pairs that do not generate variable degrees of freedom are deleted, and the variable degree of freedom generators are decomposed.

[0050] S2. Determine the expected motion of the multi-mode parallel mechanism according to the requirements of the motion simulator {S f,PM}, specifically:

[0051]

[0052] The finite motion sets of various working modes are combined to obtain the standard form of the branch chain with fixed degrees of freedom:

[0053]

[0054] The finite motion sets of various working modes are represented separately to obtain the variable degree of freedom standard form.

[0055]

[0056] S3. Based on the screw trigonometric product operation rule, a rotation / translation factor is added to the fixed-degree-of-freedom standard form, and the kinematic pair type / position replacement is performed without affecting the trigonometric product operation result to obtain a fixed-degree-of-freedom derivative, and then a fixed-degree-of-freedom branched configuration is obtained.

[0057] S4. Based on the screw trigonometric product operation rule, a rotation / translation factor is added to the variable degree of freedom standard form, and the kinematic pair type / position is replaced without affecting the trigonometric product operation result to obtain a variable degree of freedom derivative. A reasonable variable degree of freedom generator is selected from the analysis result of S1 to add to the branch chain, and the remaining kinematic pairs are integrated on this basis to obtain a variable degree of freedom branch chain configuration.

[0058] S5. Based on the assembly conditions of the multi-mode parallel mechanism, the fixed degree of freedom branch configuration and the variable degree of freedom branch configuration, a parallel mechanism that can switch working modes is constructed.

[0059] The parallel mechanism capable of switching working modes for a motion simulator of the present invention and its construction method switch the working mode through four driving sub-control mechanisms in the initial configuration, and drive the moving platform 5 relative to the fixed platform 4 to realize the movement and mutual switching between the 2T1R mode and the 2R1T mode by controlling the three moving sub-control mechanisms in each branch chain and the outer rotating sub-control mechanism of the first universal joint U1 of the first UPU branch chain 1, so as to adapt to different working environments and switch working modes, and have the advantages of strong adaptability, high rigidity, strong bearing capacity and good dynamic performance, etc. The problem that the existing parallel mechanism has a single structure and cannot meet the working requirements under complex conditions is solved.

[0060] The embodiments described above are only descriptions of the preferred implementation modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A parallel mechanism for a motion simulator capable of switching working modes, characterized in that: It includes a moving platform, a fixed platform, and a first UPU branch, a first RPU branch, and a second RPU branch arranged between the moving platform and the fixed platform. The movable platform and the fixed platform are both triangular structures, the first UPU branch chain, the first RPU branch chain, and the second RPU branch chain are respectively arranged at the edges of the corner vertices of the fixed platform, the outer rotating shaft of the second universal joint in the first UPU branch chain, the first rotating pair in the first RPU branch chain, and the second rotating pair in the second RPU branch chain are fixedly connected to the fixed platform, and the outer rotating shaft of the first universal joint in the first UPU branch chain, the third universal joint in the first RPU branch chain, and the fourth universal joint in the second RPU branch chain are fixedly connected to the movable platform; The first UPU branch chain includes a first universal joint, a first moving pair and a second universal joint, the inner rotating shaft of the second universal joint is connected to the inner rotating shaft of the first universal joint through the first moving pair, and the inner rotating axis of the second universal joint is parallel to the inner rotating axis of the first universal joint; The first RPU branch chain and the second RPU branch chain have the same structure, the first RPU branch chain includes a first rotating pair, a second moving pair and a third universal joint, the inner rotating shaft of the first rotating pair is connected to the inner rotating shaft of the third universal joint through the second moving pair, and the inner rotating shaft of the first rotating pair is parallel to the inner rotating axis of the third universal joint; the second RPU branch chain includes a second rotating pair, a third moving pair and a fourth universal joint, the inner rotating shaft of the second rotating pair is connected to the inner rotating shaft of the fourth universal joint through the third moving pair, and the inner rotating axis of the second rotating pair is parallel to the inner rotating axis of the fourth universal joint; The outer rotation axis of the first universal joint in the first UPU branch, the first rotation sub-axis in the first RPU branch, and the second rotation sub-axis in the second RPU branch are parallel to each other, the first universal joint, the third universal joint, and the fourth universal joint are respectively arranged at the corner edges of the moving platform, and the axis of the outer rotation shaft of the third universal joint is colinear with the axis of the outer rotation shaft of the fourth universal joint, and the outer rotation axis of the first universal joint is perpendicular to the outer rotation axis of the third universal joint; The first mobile pair in the first UPU branch, the second mobile pair in the first RPU branch, the third mobile pair in the second RPU branch, and the outer rotating shaft of the first universal joint of the first UPU branch serve as driving pairs. The four driving pairs drive the moving platform relative to the fixed platform to realize the movement and mutual switching of the spatial 2T1R working mode and 2R1T working mode.

2. The parallel mechanism capable of switching working modes for a motion simulator according to claim 1, characterized in that: The mechanism has a 2-RPU-UPU configuration. When the moving platform is parallel to the fixed platform and their center points are vertically collinear, the 2T1R working mode and the 2R1T working mode can be switched. There is no need to reorganize the mechanism when switching the working mode. The working mode can be switched by controlling the movement of the mechanism only in the initial position.

3. The parallel mechanism capable of switching working modes for a motion simulator according to claim 1, characterized in that: The center of the fixed platform is the coordinate origin, the direction parallel to the first rotating secondary axis in the first RPU branch chain is the x-axis, the direction parallel to the outer rotating axis axis of the third universal joint in the first RPU branch chain is the y-axis, and the direction perpendicular to the fixed platform is the z-axis.

4. The parallel mechanism capable of switching working modes for a motion simulator according to claim 1, characterized in that: The mechanism has 2R2T motions in the initial position, namely movement along the z-axis, movement along the y-axis, rotation around the y-axis and rotation around the x-axis. The first moving pair in the first UPU branch, the second moving pair in the first RPU branch, the third moving pair in the second RPU branch and the outer rotating shaft of the first universal joint of the first UPU branch serve as driving pairs. When the mechanism rotates around the y-axis, it will lose the ability to move along the y-axis, and after rotating around the y-axis, it will lose the ability to move along the y-axis direction.

5. The parallel mechanism capable of switching working modes for a motion simulator according to claim 1, characterized in that: The first moving pair, the second moving pair and the third moving pair are all composed of a sliding rod and a sliding sleeve.

6. The parallel mechanism capable of switching working modes for a motion simulator according to claim 1, characterized in that: The first universal joint, the second universal joint, the third universal joint and the fourth universal joint are all composed of two mutually perpendicular rotation axes.

7. A method for constructing a parallel mechanism capable of switching working modes for a motion simulator according to any one of claims 1 to 6, characterized in that: It includes the following steps: S1. Based on the finite screw method, the finite motion and instantaneous motion of the existing variable degree of freedom branch chain are analyzed, and the variable degree of freedom generators are decomposed; S2. Determine the expected motion of the multi-mode parallel mechanism according to the requirements of the motion simulator. f,PM }, and the fixed degree of freedom branch chain output motion {S f,IVM } standard type and variable degree of freedom branch chain output motion {S f,VM }Standard type; S3. Based on the screw trigonometric product operation rule, the fixed-degree-of-freedom derivative formula is derived according to the fixed-degree-of-freedom standard form, and then the fixed-degree-of-freedom branched chain configuration is obtained; Where θ is the rotation angle of the rigid body around the Chasles axis relative to the reference position, τ is the translation distance along the Chasles axis, s is the direction unit vector of the axis, and r is the position vector of the axis. S4. Based on the screw trigonometric product operation rule, the variable degree of freedom derivative formula is derived according to the variable degree of freedom standard form, and the variable degree of freedom generator is selected to add to the branch chain. On this basis, the remaining kinematic pairs are integrated to obtain the variable degree of freedom branch chain configuration; S5. Based on the assembly conditions of the multi-mode parallel mechanism, the fixed degree of freedom branch configuration and the variable degree of freedom branch configuration, a parallel mechanism that can switch working modes is constructed.

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