A cam-type rope wheel mechanism dynamics equivalent analysis method

Abstract

The application discloses a cam type rope wheel mechanism dynamics equivalent analysis method and relates to the technical field of mechanical simulation, and aims to provide a method capable of performing dynamics simulation analysis on an arbitrary shape cam type rope wheel mechanism, which comprises the following steps: acquiring design data of the cam type rope wheel mechanism; according to the design data, equivalently dividing a cam outer contour into a fixed component and a movable component connected with the fixed component; setting an initial position of the movable component; measuring a motion parameter limit value of the movable component according to the initial position of the movable component and the cam outer contour; and based on a multi-body dynamics simulation software, performing simulation motion on the movable component until the motion parameter of the movable component reaches the limit value, and the movable component stops moving; the method can perform dynamics equivalent analysis on an arbitrary shape cam type rope wheel mechanism, has a wider application range, and is especially suitable for a variable radius non-integral circle cam.

Description

Technical Field

[0001] This invention relates to the field of mechanical simulation technology. Background Technology

[0002] Currently, when performing equivalent simulations of cam-type rope-pulley mechanisms, existing multibody dynamics simulation software can only model complete, fixed-radius circular rope-pulley mechanisms. However, in the field of mechanics, to achieve changes in the angle of the transfer mechanism, it is necessary to design a cam-type rope-pulley mechanism. When dealing with non-circular rope-pulley mechanisms with variable radii, existing multibody dynamics simulation software cannot model or perform equivalent analysis.

[0003] Specifically, the parameters that can be set in existing multibody dynamics simulation software are roughly as follows: the number and location of fixed points in the rope wheel system, involving the position, attributes and diameter of the pulley, the starting fixed point of the rope, the winding orientation and the winding sequence of the rope. Correspondingly, the modeling steps of the rope wheel mechanism in the multibody dynamics simulation software include: (1) naming, location selection and fixed target selection of the number of fixed points of the rope in the rope wheel mechanism: that is, setting how many fixed points (anchor points) the rope has, naming the fixed points, selecting the location of the fixed points, selecting the parts that the fixed points are fixed to, and the number of fixed points will be displayed on the simulation software interface; specifically, taking two fixed anchor points of the rope as an example, labeled as 1 and 2 respectively, in the multibody dynamics simulation software, select 1 and 2 respectively and fill in the options or right-click to select the location; among them, the name is named by yourself, and the location and connecting parts can be selected by right-click; ( 2) Setting the properties of pulleys in the rope: When creating a rope, a traveling wheel or a fixed guide wheel will be built on the rope. This wheel is in contact with the rope, so that the guide wheel of the rope can roll forward on the rope. The properties of the wheel need to be set uniformly; (3) Determining the specific parameters of each pulley in the rope: Select how many pulleys there are in the rope, the name and position of each pulley, whether the rope is wrapped around the pulley from the top or the bottom, and the diameter parameter of the pulley; Specifically, when the developer enters the number of pulleys, there will be a number of prompts. The parameters of each pulley must be configured in the pulley parameter setting interface before proceeding to the next step; (4) Determine the order in which the rope is wrapped around the pulleys. At this point, the modeling of the rope wheel mechanism is completed. See the results. Figure 2 , Figure 2 The complete fixed-radius circular rope-wheel mechanism created in multibody dynamics simulation software is demonstrated.

[0004] As can be seen from the above steps, current multibody dynamics simulation software can only input a single pulley diameter parameter to set a fixed diameter value when simulating pulleys, and the default pulley shape is a fixed full circle. This means the simulation software can only model complete, fixed-radius circular rope-pulley mechanisms and cannot fit other shapes of cam-pulley mechanisms. However, due to the specific needs of real-world applications, such as weight reduction, the cam shapes we actually use are mostly composed of arc segments with unequal radii, rather than an idealized, complete circular pulley. Specifically, for example... Figure 3 As shown. For cams with irregular shapes like this, existing multibody dynamics software cannot directly express the cam's profile, nor can it fit the profile shape of a variable-radius cam, thus making it impossible to establish an equivalent simulation model of such a cam. In practical applications, however, we need to perform equivalent simulation analysis on the cam-type pulley mechanism to obtain feedback on data such as component motion speed, cam force conditions, and rope force conditions, which is crucial for the design and application of the cam-type pulley mechanism.

[0005] Therefore, how to provide a method for dynamic simulation analysis of cam-type rope pulley mechanisms of arbitrary shapes has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] To address the technical problems existing in the prior art, this invention provides a dynamic equivalent analysis method for cam-type pulley mechanisms. This method uses a movable component to equivalently divide the outer contour of the cam and restrict its movement, ultimately obtaining an equivalent model of the cam-type pulley mechanism. This method can perform dynamic equivalent analysis on cam-type pulley mechanisms of arbitrary shapes and has a wider range of applications.

[0007] A dynamic equivalent analysis method for a cam-type rope pulley mechanism, the cam-type rope pulley mechanism including a rope and a cam, the method comprising:

[0008] S1. Obtain the design data for the cam-type pulley mechanism;

[0009] S2. Based on the design data, the outer contour of the cam is equivalently divided into a fixed component and a movable component connected to the fixed component;

[0010] S3. Set the initial position of the movable component;

[0011] S4. Measure the limit values ​​of the motion parameters of the movable component based on the initial position of the movable component and the outer contour of the cam.

[0012] S5. Based on multibody dynamics simulation software, simulate the motion of the movable component until the motion parameters of the movable component reach the limit value, and then the movable component stops moving.

[0013] S6. Compare the outer contour formed by the movable component and the fixed component with the outer contour of the cam. If the contours are inconsistent, adjust the limit value of the motion parameters of the movable component and repeat step S5 until the contours are consistent, and obtain the dynamic equivalent model of the cam-type rope wheel mechanism.

[0014] Furthermore, the fixed component includes a first fixed pulley and a second fixed pulley, and the movable component includes a plurality of pulley-piston mechanisms, each pulley-piston mechanism including a movable pulley and a piston rod connected to the movable pulley.

[0015] Furthermore, the outer contour of the cam includes a straight line segment and at least one arc segment;

[0016] When dividing the outer contour of the cam into equivalent segments, the straight segments of the outer contour of the cam are equivalent to fixed components, and the arc segments of the outer contour of the cam are equivalent to movable components.

[0017] Furthermore, the design data of the cam-type rope pulley mechanism includes: rope radius, cam initial radius, and at least one cam rear half radius, wherein the cam rear half radius corresponds one-to-one with the cam outer contour arc segment.

[0018] Furthermore, the center position of the first fixed pulley is set to be the same as the rotation center position of the cam, the radius of the first fixed pulley is the same as the initial radius of the cam, and the first fixed pulley is tangent to the straight line segment of the outer contour of the cam;

[0019] The center of the second fixed pulley is set to be the same as the center of the transition circle, and the radius of the second fixed pulley is the same as the radius of the transition circle. The transition circle is the inscribed circle of the transition fillet between the straight line segment and the arc segment of the outer contour of the cam.

[0020] Furthermore, when the outer contour of the cam in the cam-type sheave mechanism is equivalently divided into movable components, the equivalent division of an arc segment of the outer contour of the cam includes the following steps:

[0021] S21. Determine the diameter of the movable pulley based on the rope radius;

[0022] S22. Offset the outer contour arc segment of the cam inward by the length of the rope radius to obtain the tangent of the movable pulley;

[0023] S23. Set up multiple movable pulleys with the diameter of the movable pulley as the diameter, the movable pulleys are tangent to each other and to the tangent of the movable pulley, until the tangent of the movable pulley is completely fitted by the movable pulley, and obtain the number of the movable pulleys;

[0024] S24. Each of the movable pulleys is connected to a piston rod, resulting in multiple pulley-piston mechanisms, which serve as the equivalent division result of the outer contour arc segment of the cam.

[0025] Furthermore, the diameter of the movable pulley is greater than 8 times the radius of the rope.

[0026] Further, setting the initial position of the movable component includes:

[0027] The rope in the cam-type rope pulley mechanism is set at the initial position, where the rope is in contact with and straightened by the straight section of the outer contour of the cam.

[0028] The pulley piston mechanism, obtained by equivalently dividing all the outer contour arc segments of the cam, is tangentially arranged on the side of the rope close to the cam. The pulley piston mechanism is arranged in order of proximity to the second fixed pulley during the equivalent division, from the closest to the second fixed pulley to the furthest from the second fixed pulley.

[0029] Each of the aforementioned pulley piston mechanisms is connected to the first fixed pulley via springs and sleeves, and the movable pulley, piston rod, spring, and sleeve are sequentially connected to the first fixed pulley.

[0030] Furthermore, the limit values ​​of the motion parameters include the limit values ​​of radial movement distance and the limit values ​​of swing angle;

[0031] When measuring the limit values ​​of the motion parameters of the movable component based on the initial position and the outer contour of the cam, the measurement of the limit values ​​of the motion parameters for a pulley-piston mechanism includes the following steps:

[0032] S41. Connect the center of the movable pulley at the initial position with the rotation center of the cam to obtain the first line segment;

[0033] S42. Connect the center of the movable pulley in the equivalent division result of step S23 with the rotation center of the cam to obtain the second line segment;

[0034] S43. A first circular arc is obtained with the rotation center of the cam as the center and the length of the second line segment as the radius;

[0035] S44. Find the intersection point of the first line segment and the first arc, and connect it to the rotation center of the cam to obtain the third line segment;

[0036] S45. The limit value of the radial movement distance is the length of the first line segment minus the length of the third line segment, and the limit value of the swing angle is the angle between the first line segment and the second line segment.

[0037] Furthermore, the limit values ​​of the motion parameters include the limit values ​​of radial movement distance and the limit values ​​of swing angle;

[0038] When the movable component is simulated to move, it simultaneously rotates and moves, specifically including:

[0039] The movable component rotates about the cam axis and moves toward the outer contour arc segment of the cam, with the maximum rotation angle being the swing angle limit value.

[0040] The movable component moves along the connection direction between the center of the movable pulley and the rotation center of the cam, and moves closer to the rotation center of the cam. The maximum moving distance is the limit value of the radial moving distance.

[0041] The dynamic equivalent analysis method for cam-type rope pulley mechanisms provided by this invention has at least the following beneficial effects:

[0042] (1) By using movable components to equivalently divide the outer contour of the cam and restrict its movement, an equivalent model of the cam-type pulley mechanism is obtained. The irregular outer contour is divided into multiple arc segments, and movable pulleys are divided for different arc segments of the cam outer contour. This enables dynamic simulation analysis of cam-type pulley mechanisms of arbitrary shapes, overcoming the limitations of multibody dynamics simulation software in modeling and simulating cam-type pulley mechanisms. This allows dynamics simulation software to perform simulation analysis on cam-type pulley mechanisms of arbitrary shapes, filling a technological gap in this field. This method can be more widely applied in the mechanical and engineering fields, especially suitable for cam-type pulley mechanisms with variable radii and non-complete circular contours.

[0043] (2) When fitting the outer contour of the cam of the rope wheel mechanism, the movable pulley with the smallest radius should be used. Selecting a movable pulley with a smaller diameter can achieve a higher precision in the division of the outer contour of the cam. Furthermore, since the rope wheel mechanism is limited by the minimum radius, the folded segment formed by the combination of multiple movable pulley tangents is closer to the outer contour of the cam. Under the premise of conforming to the structural design of the rope wheel mechanism, a higher accuracy in fitting the outer contour of the cam can be achieved. Attached Figure Description

[0044] Figure 1 A flowchart of an embodiment of the dynamic equivalent analysis method for a cam-type rope pulley mechanism provided by the present invention;

[0045] Figure 2 This is a schematic diagram of the simulation results of the rope pulley mechanism using existing multibody dynamics simulation software;

[0046] Figure 3 A schematic diagram of a cam used for equivalent analysis in an embodiment of the equivalent analysis method provided by the present invention;

[0047] Figure 4 This is a schematic diagram of an embodiment of the equivalent partitioning process of the cam outer contour in the equivalent analysis method provided by the present invention.

[0048] Figure 5A schematic diagram of one embodiment of the initial position of a movable component in the equivalent analysis method provided by the present invention;

[0049] Figure 6 A schematic diagram of an embodiment comparing the equivalent partitioning result with the initial position of a movable component in the equivalent analysis method provided by the present invention;

[0050] Figure 7 A schematic diagram of an embodiment of the equivalent analysis method provided by the present invention for measuring the limit values ​​of motion parameters of a movable component;

[0051] Reference numerals: 1-Cam, 101-Straight line segment of cam outer contour, 102-Curved line segment of cam outer contour, 2-Rope, 3-First fixed pulley, 4-Second fixed pulley, 511-First movable pulley, 521-Second movable pulley, 531-Third movable pulley, 541-Fourth movable pulley, 551-Fifth movable pulley, 561-Sixth movable pulley, 61-Initial position of first movable pulley, 62-Initial position of second movable pulley, 63-Initial position of third movable pulley, 512-First piston rod, 513-First spring, 514-First sleeve. Detailed Implementation

[0052] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0053] See Figure 1 In some embodiments, a dynamic equivalent analysis method for a cam-type rope pulley mechanism is provided, the cam-type rope pulley mechanism including a rope and a cam, the method comprising:

[0054] S1. Obtain the design data for the cam-type pulley mechanism;

[0055] S2. Based on the design data, the outer contour of the cam is equivalently divided into a fixed component and a movable component connected to the fixed component;

[0056] S3. Set the initial position of the movable component;

[0057] S4. Measure the limit values ​​of the motion parameters of the movable component based on the initial position of the movable component and the outer contour of the cam.

[0058] S5. Based on multibody dynamics simulation software, simulate the motion of the movable component until the motion parameters of the movable component reach the limit value, and then the movable component stops moving.

[0059] S6. Compare the outer contour formed by the movable component and the fixed component with the outer contour of the cam. If the contours are inconsistent, adjust the limit value of the motion parameters of the movable component and repeat step S5 until the contours are consistent, and obtain the dynamic equivalent model of the cam-type rope wheel mechanism.

[0060] Specifically, the fixed component includes a first fixed pulley and a second fixed pulley, and the movable component includes a plurality of pulley-piston mechanisms, each of which includes a movable pulley and a piston rod connected to the movable pulley.

[0061] It should be noted that the dynamic equivalent analysis method of the cam-type rope pulley mechanism is to treat the cam as multiple small pulleys of fixed circles with different radii. The initial position of these small pulleys is not exactly on the contour of the cam, but is tangent to the rope. As the rope moves, the small pulleys move along the line connecting the small pulley and the rotation center of the cam and swing around the rotation center of the cam. By setting the limit values ​​of radial movement distance and swing angle, the small pulleys stop moving when they reach the corresponding position on the outer contour of the cam. In this way, the outer contour of the cam can be equivalently represented.

[0062] See Figure 3 The cam outer contour includes a straight segment 101 and at least one curved segment 102. When equivalently dividing the cam outer contour, the straight segment is equivalent to a fixed component, and the curved segment is equivalent to a movable component. The straight segment is the straight outer contour portion of the cam that contacts the rope.

[0063] In step S1, the design data of the cam-type rope pulley mechanism includes: rope radius, cam initial radius, and at least one cam rear half radius, wherein the cam rear half radius corresponds one-to-one with the cam outer contour arc segment. Specifically, the cam initial radius is the radius of a circle centered at the cam rotation center and tangent to the straight line segment of the cam outer contour, and the cam rear half radius is the radius of the circle containing the cam outer contour arc segment.

[0064] Step S2 further includes setting the positions of the first and second fixed pulleys. Specifically, the center of the first fixed pulley is set to be the same as the rotation center of the cam, the radius of the first fixed pulley is the same as the initial radius of the cam, and the first fixed pulley is tangent to the straight line segment of the outer contour of the cam; the center of the second fixed pulley is set to be the same as the center of the transition circle, and the radius of the second fixed pulley is the same as the radius of the transition circle, wherein the transition circle is the inscribed circle of the transition fillet between the straight line segment and the arc segment of the outer contour of the cam.

[0065] In step S2, when the outer contour of the cam in the cam-type pulley mechanism is equivalently divided into movable components, the equivalent division of an arc segment of the outer contour of a cam includes the following steps:

[0066] S21. Determine the diameter of the movable pulley based on the rope radius;

[0067] S22. Offset the outer contour arc segment of the cam inward by the length of the rope radius to obtain the tangent of the movable pulley;

[0068] S23. Set up multiple movable pulleys with the diameter of the movable pulley as the diameter, the movable pulleys are tangent to each other and to the tangent of the movable pulley, until the tangent of the movable pulley is completely fitted by the movable pulley, and obtain the number of the movable pulleys;

[0069] S24. Each of the movable pulleys is connected to a piston rod, resulting in multiple pulley-piston mechanisms, which serve as the equivalent division result of the outer contour arc segment of the cam.

[0070] It should be noted that, theoretically, the smaller the diameter of the movable pulley, the better. However, multibody dynamics software has a minimum requirement for the diameter of the movable pulley, which is greater than 8 times the pulley groove depth. In cam-type rope pulley mechanisms, the pulley groove depth is set to the rope radius. For different cam outer contour arc segments, the equivalent circles corresponding to the contour arc segments have different radii, and movable pulleys of different radii can be used for equivalent representation. There is no limit to the number of movable pulleys; generally, two small pulleys are kept at a relatively small distance or tangent to each other.

[0071] In a preferred embodiment, the diameter of the movable pulley is greater than 8 times the radius of the rope. Selecting a movable pulley with a smaller diameter allows for more precise cam contour segmentation, and the folded segment formed by combining the tangents of multiple movable pulleys more closely approximates the cam's outer contour, resulting in higher fitting accuracy.

[0072] In step S3, setting the initial position of the movable component includes:

[0073] S31. Set the rope in the cam-type rope pulley mechanism to the initial position of the rope, wherein the initial position of the rope is when the rope is in contact with and straightened by the straight section of the outer contour of the cam.

[0074] S32. The pulley piston mechanism obtained by equivalently dividing all the outer contour arc segments of the cam is tangentially arranged on the side of the rope close to the cam. The pulley piston mechanism is arranged in order of proximity to the second fixed pulley during the equivalent division, from the closest to the second fixed pulley to the furthest from the second fixed pulley.

[0075] S33. Connect each of the pulley piston mechanisms to the first fixed pulley via springs and sleeves, and connect the movable pulley, piston rod, spring, sleeve and the first fixed pulley in sequence.

[0076] In step S31, the initial position of the rope is shown below. Figure 5As shown, the rope is attached to and straightened along the straight section of the outer contour of the cam, that is, the rope is tangentially wrapped around the first fixed pulley 3 and the second fixed pulley 4, and extended and straightened along the tangential direction, based on which the initial position of the movable component is determined.

[0077] See Figure 6 In step S32, the pulley-piston mechanisms obtained in step S2 by equivalently representing all the outer contour arc segments 102 of the cam are sequentially arranged at the tangent positions of the rope. Using the second fixed pulley 4 as a reference, in step S2, the equivalent pulley-piston mechanisms are arranged sequentially from near to far; correspondingly, in step S32, the pulley-piston mechanisms are arranged in the initial state of the rope from bottom to top in the appropriate order, with arbitrary gaps allowed between any two movable pulleys. In the initial state, the centers of the movable pulleys are all located on a straight line offset from the cam side by the radius of the corresponding movable pulley along the straight line containing rope 2. Figure 6 In the middle, starting from the second fixed pulley 4 along the rope 2, the initial positions of the first movable pulley 61, the second movable pulley 62, and the third movable pulley 63 are from bottom to top.

[0078] In a preferred embodiment, the motion parameter limits include the radial movement distance limit and the swing angle limit.

[0079] See Figure 7 C 30 C3 is the center of the movable pulley at the initial position, C4 is the center of the movable pulley in the equivalent partitioning result, and L1 is the center of the movable pulley at the initial position. 30 The line segment connecting the cam's rotation center, L2, is the line segment connecting the center of the movable pulley C3 and the cam's rotation center C1 in the equivalent partitioning result; L3 is an arc with the cam center as the center and L2 as the radius; C is the intersection of L1 and L3; L4 is the line connecting C and the cam's rotation center C1; L is the line segment connecting C and C... 30 The line connecting L and L4 has a length that is the limit of the radial movement distance, which is the difference between the lengths of L1 and L4. The value of θ3 is the angle between L1 and L2, which is the limit of the swing angle.

[0080] In step S4, when measuring the motion parameter limit values ​​of the movable component based on the initial position and the outer contour of the cam, the measurement of the motion parameter limit values ​​for a pulley-piston mechanism includes the following steps:

[0081] S41. Position the center of the movable pulley C at the initial position. 30 The first line segment L1 is obtained by connecting it to the rotation center of the cam;

[0082] S42. Connect the center of the movable pulley C3 in the equivalent division result of step S23 with the rotation center of the cam to obtain the second line segment L2.

[0083] S43. With the cam rotation center C1 as the center and the length of the second line segment as the radius, a first circular arc L3 is obtained;

[0084] S44. Find the intersection point of the first line segment L1 and the first arc L3, and connect it with the rotation center C1 of the cam to obtain the third line segment L4;

[0085] S45. The limit value of the radial movement distance is the length of the first line segment L1 minus the length of the third line segment L4, and the limit value of the swing angle is the angle θ3 between the first line segment L1 and the second line segment L2.

[0086] In step S5, when simulating the motion of the movable component, the movable component simultaneously rotates and moves, specifically including:

[0087] The movable component rotates about the cam axis and moves toward the outer contour arc segment of the cam, with the maximum rotation angle being the swing angle limit value.

[0088] The movable component moves along the connection direction between the center of the movable pulley and the rotation center of the cam, and moves closer to the rotation center of the cam. The maximum moving distance is the limit value of the radial moving distance.

[0089] In a specific application scenario, a particular cam-type pulley mechanism will be used as an example for illustration. (See [link]) Figure 3 The cam's outer contour is a pulley with a non-uniform radius and not a complete circle. The cam's outer contour includes a straight segment 101 and an arc segment 102. The initial radius R0 of the cam is 19mm, and the radius R1 of the latter half is 62mm. The cam's outer contour is equivalent to two fixed pulleys and a six movable and oscillating pulley-piston mechanism, such as... Figure 4 As shown, each pulley-piston mechanism includes a movable pulley and a piston rod. The first fixed pulley 3 is used for the tangent circle profile at the equivalent initial radius R0, and the second fixed pulley 4 is used for the transition fillet profile between the equivalent initial radius and the latter half of the radius. These two pulleys are fixed in place. See also... Figure 5In the first to sixth piston-pulley mechanisms, when the movable pulleys are in their initial positions, they are tangent to the rope 2 connecting the first fixed pulley 3 and the second fixed pulley 4. The piston rods are distributed along the line connecting the center of each movable pulley to the center of the first fixed pulley 3 (i.e., the cam rotation center). As the mechanism moves, the pulley-piston mechanism moves and rotates accordingly with the rope. When it reaches the predetermined moving distance and rotation angle, it is fixed on the outer contour line of the cam, effectively representing the cam's contour. Specifically, the process of equivalently dividing the outer contour is performed in 3D software. Multiple pulleys are used to divide the cam's contour line. In the initial state, the contour line that the rope 2 can reach (i.e., the straight line segment of the cam's outer contour) is simulated by the first fixed pulley 3 and the second fixed pulley 4. The contour line that the rope 2 cannot reach in the initial state (i.e., the arc segment of the cam's outer contour) is simulated by the movable pulley. First, the arc segment of the cam's outer contour is offset inward by the rope radius to create... Figure 6 The tangent of the movable pulley is shown. Then, the movable pulley tangent is shifted towards the center of the cam by the radius of the movable pulley. The resulting trajectory line of the final center of the movable pulley is the preset trajectory line. The equivalent movable pulley contour line can then be drawn based on this, and the movable pulley contour line is tangent to the movable pulley tangent.

[0090] After completing the equivalent division, set the initial position of the movable pulley. The initial position of the movable pulley is tangent to the initial state of the rope. A guide wheel is set at the end of the rope away from the second fixed pulley 4, which is used to pull the rope for simulated motion in subsequent steps. Distribute these movable pulleys on the section of rope between the second fixed pulley 4 and the guide wheel, as follows: Figure 5 As shown, along the initial state of the rope, from bottom to top, the movable pulleys are arranged according to their numbers: first pulley piston mechanism 51, second pulley piston mechanism 52, third pulley piston mechanism 53, fourth pulley piston mechanism 54, fifth pulley piston mechanism 55, and sixth pulley piston mechanism 56 (some mechanisms are omitted in the figure). Arbitrary gaps can be left between any two pulleys, but no movable pulley can exceed the guide wheel. In the initial state, the center of the movable pulley is located at the distance of the rope offset towards the cam corresponding to the radius of the movable pulley. Based on the initial position of the movable pulleys and the cam design data, the radial movement distance limit and the swing angle limit value corresponding to each movable pulley are measured.

[0091] See Figure 4Each pulley-piston mechanism is connected to the first fixed pulley via a spring and a sleeve. The movable pulley, piston rod, spring, and sleeve are sequentially connected to the first fixed pulley. For example, the first pulley-piston mechanism 51 is sequentially connected to the first piston rod 512, the first spring 513, the first sleeve 514, and the first fixed pulley 3. The piston rod is used to facilitate the creation of the movable pulley's movement. In the simulation system, a cylinder of arbitrary distance is drawn from the wheel center C30 of the first movable pulley's initial position along the line connecting it to the cam's rotation center C1 to represent the piston rod. The sleeve is used to facilitate the creation of the movable pulley's rotation. In the simulation system, a cylinder of arbitrary distance is drawn from the cam's rotation center C1 along the line connecting it to the wheel center C30 of the first movable pulley's initial position to represent the sleeve. The spring connects the piston rod and the sleeve, with its stiffness set to a minimum; the spring only serves to connect the piston rod and the sleeve. The system also requires the creation of prismatic and rotary joints. The prismatic joint is used to control the movement of the piston. A prismatic joint is created at the center point of the piston rod, moving along the line connecting the center of the piston rod and the center of the sleeve. The rotary joint is used to control the rotation of the sleeve. A rotary joint between the piston rod and the movable pulley is created at the center of rotation of the cam. The direction of the rotary joint is along the axial direction of the movable pulley.

[0092] After establishing the aforementioned components in the simulation system, it is necessary to set movement limits and swing limits. Movement limits are created using ForceVector to set the limit value of the radial movement distance of the movable pulley. Specifically, a ForceVector is created at the center of the piston rod and sleeve. The X-direction of movement can be set to the axis of the piston rod, and the limit value is set in the X-direction, with other directions set to 0. Alternatively, other directions can be set as limit directions. Swing limits are created using GeneralForce. A General Force is created at the rotation center of the cam and sleeve and movable pulley. The X-direction of rotation can be set to the rotation direction of the sleeve's rotary joint, and the swing angle limit value is set in the X-direction, with other directions set to 0. Alternatively, other rotation directions can be set as swing limit directions.

[0093] Create a cam-type rope pulley mechanism using the Cable command. Create the individual pulleys, with the rope wound in the following order: initial position of the third movable pulley, initial position of the second movable pulley, initial position of the first movable pulley, initial position of the second fixed pulley, and initial position of the first fixed pulley. The initial positions of the third, second, and first movable pulleys are all fixedly connected to their respective piston rods. The first and second fixed pulleys are fixedly connected to the cam support. The movable pulleys remain tangent to the rope and move and swing simultaneously under the action of the rope. Each movable pulley stops moving and remains fixed when it reaches its preset radial movement distance limit and swing angle limit. When all movable pulleys reach their motion parameter limits, the movable and fixed components form the dynamic equivalent model of the cam-type rope pulley mechanism. At this point, since there may be some deviations during the actual simulation motion, it is necessary to compare whether the outer contours formed by the movable and fixed components are consistent with the outer contour of the cam. If there is a discrepancy, the radial movement distance limit and the swing angle limit are adjusted according to the actual deviation. Then, the simulation motion is repeated based on the adjusted parameters until the outer contour is consistent, thus obtaining the final required dynamic equivalent model of the cam-type pulley mechanism. That is, by using fixed pulleys and movable pulleys to represent cam-type pulley mechanisms with variable radii and non-circular shapes, the equivalent analysis of cam-type pulley mechanisms of arbitrary shapes is realized.

[0094] The dynamic equivalent analysis method for cam-type pulley mechanisms provided in this embodiment uses movable components to equivalently divide the outer contour of the cam and restrict its movement, ultimately obtaining an equivalent model of the cam-type pulley mechanism. The irregular outer contour is divided into multiple arc segments, and movable pulleys are used to divide different arc segments of the cam's outer contour. This allows for dynamic simulation analysis of cam-type pulley mechanisms of arbitrary shapes, overcoming the limitations of multibody dynamics simulation software in modeling and simulating cam-type pulley mechanisms. It enables dynamics simulation software to perform simulation analysis on cam-type pulley mechanisms of arbitrary shapes, filling a technological gap in this field. This method can be more widely applied in the mechanical and engineering fields, especially suitable for cam-type pulley mechanisms with variable radii and non-complete circular contours. When fitting the outer contour of the cam in the pulley mechanism, movable pulleys with the smallest possible radius are used. Since the pulley mechanism structure limits the radius to a minimum, selecting movable pulleys with smaller diameters achieves higher accuracy in dividing the cam's outer contour. The folded segments formed by combining the tangents of multiple movable pulleys more closely approximate the cam's outer contour, achieving higher cam outer contour fitting accuracy while adhering to the pulley mechanism's structural design.

[0095] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A dynamic equivalent analysis method for a cam-type rope pulley mechanism, wherein the cam-type rope pulley mechanism includes a rope and a cam, characterized in that, The method includes: S1. Obtain the design data for the cam-type pulley mechanism; S2. Based on the design data, the outer contour of the cam is equivalently divided into a fixed component and a movable component connected to the fixed component; S3. Set the initial position of the movable component; S4. Measure the limit values ​​of the motion parameters of the movable component based on the initial position of the movable component and the outer contour of the cam. S5. Based on multibody dynamics simulation software, simulate the motion of the movable component until the motion parameters of the movable component reach the limit value, and then the movable component stops moving. S6. Compare the outer contour formed by the movable component and the fixed component with the outer contour of the cam. If the contours are inconsistent, adjust the limit value of the motion parameters of the movable component and repeat step S5 until the contours are consistent, and obtain the dynamic equivalent model of the cam-type rope wheel mechanism. When the outer contour of the cam is equivalently divided into movable components, the equivalent division of an arc segment of the outer contour of the cam includes the following steps: S21. Determine the diameter of the movable pulley based on the rope radius; S22. Offset the outer contour arc segment of the cam inward by the length of the rope radius to obtain the tangent of the movable pulley; S23. Set up multiple movable pulleys with the diameter of the movable pulley as the diameter, the movable pulleys are tangent to each other and to the tangent of the movable pulley, until the tangent of the movable pulley is completely fitted by the movable pulley, and obtain the number of the movable pulleys; S24. Each of the movable pulleys is connected to a piston rod, resulting in multiple pulley-piston mechanisms, which serve as the equivalent division result of the outer contour arc segment of the cam. The limit values ​​of the motion parameters include the limit values ​​of radial movement distance and swing angle; When measuring the limit values ​​of the motion parameters of the movable component based on the initial position and the outer contour of the cam, the measurement of the limit values ​​of the motion parameters for a pulley-piston mechanism includes the following steps: S41. Connect the center of the movable pulley at the initial position with the rotation center of the cam to obtain the first line segment; S42. Connect the center of the movable pulley in the equivalent division result of step S23 with the rotation center of the cam to obtain the second line segment; S43. A first circular arc is obtained with the rotation center of the cam as the center and the length of the second line segment as the radius; S44. Find the intersection point of the first line segment and the first arc, and connect it to the rotation center of the cam to obtain the third line segment; S45. The limit value of the radial movement distance is the length of the first line segment minus the length of the third line segment, and the limit value of the swing angle is the angle between the first line segment and the second line segment.

2. The method according to claim 1, characterized in that, The fixed component includes a first fixed pulley and a second fixed pulley, and the movable component includes a plurality of pulley-piston mechanisms, each of which includes a movable pulley and a piston rod connected to the movable pulley.

3. The method according to claim 1, characterized in that, The outer contour of the cam includes a straight line segment and at least one arc segment; When dividing the outer contour of the cam into equivalent segments, the straight segments of the outer contour of the cam are equivalent to fixed components, and the arc segments of the outer contour of the cam are equivalent to movable components.

4. The method according to claim 1, characterized in that, The design data of the cam-type rope pulley mechanism includes: rope radius, cam initial radius, and at least one cam rear half radius, wherein the cam rear half radius corresponds one-to-one with the cam outer contour arc segment.

5. The method according to claim 2, characterized in that, The center of the first fixed pulley is set to be the same as the rotation center of the cam, the radius of the first fixed pulley is the same as the initial radius of the cam, and the first fixed pulley is tangent to the straight line segment of the outer contour of the cam. The center of the second fixed pulley is set to be the same as the center of the transition circle, and the radius of the second fixed pulley is the same as the radius of the transition circle. The transition circle is the inscribed circle of the transition fillet between the straight line segment and the arc segment of the outer contour of the cam.

6. The method according to claim 1, characterized in that, The diameter of the movable pulley is greater than 8 times the radius of the rope.

7. The method according to claim 2, characterized in that, Setting the initial position of the movable component includes: The rope in the cam-type rope pulley mechanism is set at the initial position, where the rope is in contact with and straightened by the straight section of the outer contour of the cam. The pulley piston mechanism, which is obtained by equivalently dividing all the outer contour arc segments of the cam, is tangentially arranged on the side of the rope close to the cam. The pulley piston mechanism is arranged in order of proximity to the second fixed pulley during the equivalent division, from the closest to the second fixed pulley to the furthest from the second fixed pulley. Each of the aforementioned pulley piston mechanisms is connected to the first fixed pulley via springs and sleeves, and the movable pulley, piston rod, spring, and sleeve are sequentially connected to the first fixed pulley.

8. The method according to claim 2, characterized in that, The limit values ​​of the motion parameters include the limit values ​​of radial movement distance and swing angle; When the movable component is simulated to move, it simultaneously rotates and moves, specifically including: The movable component rotates about the cam axis and moves toward the outer contour arc segment of the cam, with the maximum rotation angle being the swing angle limit value. The movable component moves along the connection direction between the center of the movable pulley and the rotation center of the cam, and moves closer to the rotation center of the cam. The maximum moving distance is the limit value of the radial moving distance.

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