A spatial six-degree-of-freedom motion simulation device and control system

Abstract

The application discloses a kind of space six degrees of freedom motion simulation device and control system, specifically related to motion simulation technical field, it includes: workbox and the support foot of setting at its bottom.The environmental simulation compensation module inputs the fluid damping force model as disturbance feedforward into position control module and is compensated in real time by disturbance observer, six cable parallel mechanism tension equalization algorithm dynamically adjusts the torque limit value of each servo driver to prevent steel wire rope slack or overload, realizes the double closed-loop servo positioning control architecture with position loop as leading and visual feedback as correction, effectively solves the technical defects that single encoder feedback exists cumulative error and open-loop vision system response lag, ensure that system can still realize micron level high-precision positioning and long time steady-state residence under complex fluid damping boundary condition, significantly improve the control precision, response speed and running stability of six degrees of freedom motion simulation.

Description

Technical Field

[0001] This invention relates to the field of motion simulation technology, and in particular to a spatial six-degree-of-freedom motion simulation device and control system. Background Technology

[0002] Six-degree-of-freedom motion simulation technology is an indispensable key testing method in fields such as shipbuilding, marine engineering, and aerospace. It is primarily used to reproduce and verify the dynamic response characteristics of floating structures in complex marine environments. With the trend towards larger ships and more sophisticated marine engineering equipment, higher demands are placed on the accuracy, degrees of freedom, and environmental simulation capabilities of motion simulation systems. This technology is mainly applied in scenarios such as performance testing of ship mooring systems, verification of offshore platform positioning capabilities, ship maneuverability simulation, and the development of maritime simulators. Traditional motion simulation devices typically employ mechanical linkages, hydraulic drive platforms, or parallel electric cylinder mechanisms to achieve multi-degree-of-freedom motion. However, in recent years, rope-driven parallel robot technology has gained widespread attention and application in the field of motion simulation due to its advantages such as large workspace, high load-bearing capacity, and fast dynamic response.

[0003] However, existing technologies have limitations in practical applications. Traditional motion simulation devices often employ single-cable traction or simple multi-cable parallel traction methods, failing to form statically indeterminate, strongly coupled parallel traction systems. This makes it difficult to achieve complex six-degree-of-freedom spatial attitude simulations, particularly in coupled motions involving rotational and translational degrees of freedom. Existing position feedback systems primarily rely on rotary encoders mounted on the motor shaft, obtaining load position information through transmission ratio calculations. This indirect measurement method suffers from accumulated transmission errors and insufficient compensation for wire rope elastic deformation, making it difficult to achieve micron-level positioning accuracy. Some systems using visual feedback... Most existing systems employ open-loop control or simple visual verification, lacking control strategies that weight and deeply integrate visual feedback with encoder feedback. This results in lag in system response or unstable accuracy. Existing environmental simulation units are functionally limited and cannot accurately simulate complex boundary conditions such as fluid damping and frictional resistance experienced by a ship in water by adjusting fluid media or contact surface characteristics, leading to significant deviations between experimental results and actual operating conditions. In multi-axis collaborative control, current technologies lack effective real-time inverse kinematics calculation capabilities and tension balancing algorithms, easily leading to problems such as wire rope slack, overload, or singular system configurations, affecting motion stability and safety. Therefore, we provide a spatial six-degree-of-freedom motion simulation device and control system. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a spatial six-degree-of-freedom motion simulation device and control system.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A spatial six-degree-of-freedom motion simulation device and control system includes: a work box and support legs disposed at its bottom; The top of the working box is symmetrically arranged with six sets of expansion and contraction motors. The output end of each set of expansion and contraction motors is connected to a wire rope drum. The test space is equipped with a gantry structure composed of a mounting frame and a connecting frame. A double wheel and a single wheel are slidably mounted on the mounting frame. After the wire rope is led out from the drum, it passes through the high-precision guide rollers on the double wheel or single wheel in sequence, and the end is connected to the object under test through a universal joint; a special glass platform is provided in the middle of the working box, and a placement platform is provided above the glass platform to support the object under test. A camera and a fill light are installed at the center of the crossbeam of the connecting frame. The optical axis of the camera is perpendicular to the object being tested on the placement platform. A matte acrylic plate is fixed to the top of the object being tested. Optical positioning marks are engraved on the surface of the matte acrylic plate. A configurable counterweight module for simulating different load conditions and center of gravity positions is also provided on the side of the work box.

[0006] The present invention is further configured to include: a main control unit, a drive execution unit, a primary position feedback unit, and a visual monitoring unit; The main control unit is connected to the drive execution unit via an industrial real-time bus. The drive execution unit includes a servo driver and a permanent magnet synchronous servo motor that are electrically connected to the six sets of zoom motors in a one-to-one correspondence. The primary position feedback unit is composed of a high-resolution rotary encoder installed on the shaft end of each servo motor, which is used to collect the angular displacement of the motor in real time and convert it into the linear displacement of the wire rope through the transmission ratio. The visual monitoring unit includes the camera, a fill light, and a streaming media converter. The streaming media converter transmits the image data collected by the camera to the main control unit in real time. The main control unit integrates a position control module and a visual calculation module to construct a closed-loop servo positioning control architecture with position loop as the main driver and visual feedback as the verification and correction.

[0007] The present invention is further configured such that: the position control module of the main control unit is configured to execute the following control logic: receive the target position coordinate parameters set by the host computer, and convert them into a position setpoint recognizable by the control system; acquire the current actual position transmitted by the primary position feedback unit in real time, and calculate the position error between the position setpoint and the current actual position; perform real-time calculation based on the magnitude and direction of the position error using a preset PID control algorithm and a feedforward compensation algorithm to generate a corresponding speed command or torque command; convert the speed command or torque command into ±V analog signals or pulse / bus communication digital commands, and output them to the corresponding servo driver.

[0008] The invention is further configured such that: after receiving the control command output by the main control unit, the servo driver's internal speed loop and torque loop work together to generate a three-phase PWM waveform with precise controllable frequency and amplitude using space vector pulse width modulation technology; the permanent magnet synchronous servo motor receives the three-phase current driven by the three-phase PWM waveform to generate precise electromagnetic torque; the electromagnetic torque is amplified by a reducer and then transmitted to the wire rope drum, converting the rotational motion into the linear traction force of the wire rope, driving the object under test to move along a preset trajectory in three-dimensional space; the traction force of the wire rope and the guide roller support points of the double wheel and single wheel form a statically indeterminate strongly coupled parallel traction mechanical model, realizing coordinated driving of six degrees of freedom attitude.

[0009] The invention is further configured such that: the visual calculation module is configured to execute micron-level precision positioning logic; when the primary position feedback unit detects that the object under test is approaching the target position and the movement speed drops to a preset threshold, the main control unit automatically switches the control weights to increase the feedback priority of the visual monitoring unit; the camera continuously acquires images of optical positioning markers on the matte acrylic plate on top of the object under the auxiliary illumination of the supplementary light; the visual calculation module performs sub-pixel-level edge extraction and feature matching on the images to calculate the absolute spatial coordinates of the center of the markers; the absolute spatial coordinates are compared with the target set position, and if the error exceeds the micron-level tolerance band, a fine-tuning compensation command is generated and superimposed on the original speed command to drive the servo motor to perform low-amplitude high-frequency correction until the error is stably converged within the tolerance band.

[0010] The invention is further configured such that: the main control unit is embedded with a six-wire parallel mechanism inverse kinematics calculation module, which is used to map the six-degree-of-freedom pose matrix of the target position into the length changes and tension distribution coefficients of the six wire ropes; the inverse kinematics calculation module monitors the feedback data of each rotary encoder in real time, and performs velocity mapping and singular configuration avoidance through Jacobian matrix; when the tension difference between any two wire ropes exceeds the safety threshold, the main control unit automatically triggers the tension equalization algorithm to dynamically adjust the torque limit value of each servo drive to prevent the wire ropes from slack or overloaded and breaking, and to ensure the stiffness and motion stability of the parallel traction system.

[0011] The invention is further configured such that: the control system also includes an environmental simulation compensation module, which is linked to the specially designed glass platform and the placement platform; the bottom of the specially designed glass platform integrates a fluid supply and contact surface characteristic adjustment mechanism; the environmental simulation compensation module dynamically adjusts the fluid medium flow rate or contact surface friction coefficient according to the load conditions and center of gravity position parameters of the object under test, so as to reproduce the fluid damping and frictional resistance boundary conditions experienced by the hull in water; the environmental simulation compensation module inputs the damping force model as a disturbance feedforward quantity to the position control module, introduces a disturbance observer into the control algorithm, and performs real-time compensation for the positioning lag caused by fluid damping, thereby improving the dynamic tracking accuracy.

[0012] The invention is further configured such that: the main control unit is also equipped with a position holding and adaptive compensation module; when the vision calculation module confirms that the absolute position error is stable within the micron-level tolerance zone, the main control unit outputs a position signal and controls each servo driver to switch to torque holding mode, outputting a holding torque that is balanced with the current load gravity component and residual tension; during the holding period, the vision monitoring unit continuously monitors the position drift in a low-frequency sampling mode. If the position deviation caused by temperature deformation or wire rope creep is detected to accumulate beyond a set threshold, the adaptive compensation module automatically triggers a micro-twist and release rope command to perform closed-loop position reset, achieving long-term high-precision steady-state dwell.

[0013] The present invention is further configured such that: the streaming media converter adopts a gigabit Ethernet interface and a hardware-level image preprocessing chip to perform distortion correction, brightness equalization and ROI region cropping on the original image acquired by the camera, and transmits the compressed redundant data to the main control unit through a low-latency industrial Ethernet protocol; the position control module, vision calculation module and servo driver of the main control unit communicate with each other via EtherCAT or PROFINET IRT real-time Ethernet bus to ensure that the multi-axis synchronous control cycle is ≤ms, the timestamps of the vision feedback data and the control commands are strictly aligned, and the impact of communication jitter on the micron-level positioning accuracy is eliminated.

[0014] The invention is further configured such that: the system is equipped with a dual-redundant safety monitoring architecture; the main control unit compares the encoder data of the primary position feedback unit with the absolute coordinate data of the vision calculation module in real time; when the deviation between the two continuously exceeds the dynamic tolerance range, it is determined that the sensor is faulty or the wire rope is slipping, and the emergency stop logic is immediately triggered and the servo driver is locked; the zoom motor is equipped with a mechanical brake device; the control system automatically activates the brake in the event of a power failure or serious fault, and forms a three-level protection through the physical hard limit of the limit frame and the mounting plate; the control algorithm has built-in soft limit and acceleration look-ahead planning functions, and automatically and smoothly decelerates when approaching the boundary of the test space to prevent rigid collision damage to the precision guide roller and the object under test.

[0015] The beneficial effects of this invention are as follows: 1. This invention uses an inverse kinematics calculation module within the main control unit to map the six-degree-of-freedom pose matrix of the target position into the length changes and tension distribution coefficients of six steel wire ropes in real time. The position control module employs a PID algorithm and a feedforward compensation algorithm to perform high-speed closed-loop control on the encoder data transmitted by the primary position feedback unit. When the measured object approaches the target position, the visual calculation module automatically increases the feedback priority of the visual monitoring unit. By extracting sub-pixel-level edges and matching features from the images acquired by the camera, the absolute spatial coordinates are calculated, and fine-tuning compensation commands are generated for low-amplitude, high-frequency correction. Simultaneously, the environmental simulation compensation module incorporates fluid damping force... The model serves as the position control module for disturbance feedforward input and is compensated in real time through a disturbance observer. The tension balancing algorithm of the six-cable parallel mechanism dynamically adjusts the torque limit value of each servo drive to prevent wire rope slack or overload. Ultimately, a dual closed-loop servo positioning control architecture with position loop as the main driver and visual feedback as the verification and correction is realized. This effectively solves the technical defects of cumulative error in single encoder feedback and response lag in open-loop vision system. It ensures that the system can still achieve micron-level high-precision positioning and long-term steady-state dwell under complex fluid damping boundary conditions, significantly improving the control accuracy, response speed and operation stability of six-degree-of-freedom motion simulation.

[0016] 2. This invention uses six sets of retractable motors symmetrically distributed around the top of the work box to drive a wire rope drum. The wire rope passes sequentially around high-precision guide rollers on a double-wheel and single-wheel mounted on the mounting frame before connecting to the object under test, forming a statically indeterminate, strongly coupled parallel traction structure. A camera and supplementary light mounted at the center of the connecting frame beam capture real-time images of optical positioning markers on the matte acrylic plate on top of the object under test. Simultaneously, a specially designed glass platform below the object under test simulates fluid damping boundary conditions by adjusting the fluid medium or contact surface characteristics. A counterweight module can be configured to simulate different load conditions and center of gravity positions. Ultimately, this invention achieves accurate reproduction and micron-level positioning testing of the object under test's six degrees of freedom motion in three-dimensional space. This effectively solves the technical problems of traditional single-cable traction failing to simulate complex attitudes and lacking positioning accuracy, significantly improving the simulation accuracy and reliability of dynamic behavior testing for floating structures such as ships. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the system framework in this invention. Figure 2 This is a schematic diagram of the overall device in this invention.

[0018] Figure 3 This is a partial disassembly diagram of the present invention.

[0019] Figure 4 This is a partial schematic diagram of the double-wheel mechanism and the single-wheel mechanism in this invention.

[0020] Figure 5 This is a partial schematic diagram of the mounting bracket and connecting bracket in this invention.

[0021] 1. Working box; 2. Support feet; 3. Expansion / retraction motor; 4. Traction wire; 5. Mounting plate; 6. Support rod; 7. Double wheel assembly; 8. Single wheel assembly; 9. Limiting frame; 10. Placement platform; 11. Mounting frame; 12. Connecting frame; 13. Camera; 14. Fill light; 15. Streaming media converter. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Example 1

[0023] like Figure 1 As shown, a spatial six-degree-of-freedom motion control system includes: a main control unit, a drive execution unit, a primary position feedback unit, and a vision monitoring unit; The main control unit communicates with the drive execution unit via an industrial real-time bus. The drive execution unit includes servo drivers and permanent magnet synchronous servo motors that are electrically connected to the six sets of zoom motors 3 in a one-to-one correspondence. The primary position feedback unit consists of a high-resolution rotary encoder installed on the shaft end of each servo motor, which is used to collect the angular displacement of the motor in real time and convert it into the linear displacement of the wire rope through the transmission ratio. The visual monitoring unit includes a camera 13, a fill light 14, and a streaming media converter 15. The streaming media converter 15 transmits the image data collected by the camera 13 to the main control unit in real time. The main control unit integrates a position control module and a visual calculation module to build a closed-loop servo positioning control architecture with position loop as the main driver and visual feedback as the verification and correction. The position control module of the main control unit is configured to execute the following control logic: receive the target position coordinate parameters set by the host computer and convert them into a position setpoint that the control system can recognize; acquire the current actual position transmitted by the primary position feedback unit in real time and calculate the position error between the position setpoint and the current actual position; perform real-time calculation based on the magnitude and direction of the position error using a preset PID control algorithm and feedforward compensation algorithm to generate the corresponding speed command or torque command; convert the speed command or torque command into ±10V analog signal or pulse / bus communication digital command and output it to the corresponding servo driver. After receiving the control command output by the main control unit, the servo driver's internal speed loop and torque loop work together to generate a three-phase PWM waveform with precise controllable frequency and amplitude using space vector pulse width modulation technology. The permanent magnet synchronous servo motor receives the three-phase current driven by the three-phase PWM waveform and generates precise electromagnetic torque. The electromagnetic torque is amplified by the reducer and then transmitted to the wire rope drum, converting the rotational motion into the linear traction force of the wire rope, driving the measured object to move along a preset trajectory in three-dimensional space. The traction force of the wire rope and the guide roller support points of the double wheel 7 and the single wheel 8 form a statically indeterminate strongly coupled parallel traction mechanical model, realizing coordinated driving of six degrees of freedom attitude. The visual calculation module is configured to execute micron-level precision positioning logic: when the primary position feedback unit detects that the object under test is approaching the target position and the movement speed drops to a preset threshold, the main control unit automatically switches the control weight and increases the feedback priority of the visual monitoring unit; under the auxiliary illumination of the supplementary light 14, the camera 13 continuously acquires images of optical positioning markers on the matte acrylic plate on the top of the object under test; the visual calculation module performs sub-pixel-level edge extraction and feature matching on the image to calculate the absolute spatial coordinates of the center of the marker; the absolute spatial coordinates are compared with the target set position, and if the error exceeds the micron-level tolerance band, a fine-tuning compensation command is generated and superimposed on the original speed command to drive the servo motor to perform low-amplitude high-frequency correction until the error is stably converged within the tolerance band; The main control unit is embedded with a six-wire parallel mechanism inverse kinematics calculation module, which maps the six-degree-of-freedom pose matrix of the target position to the length changes and tension distribution coefficients of the six wire ropes. The inverse kinematics calculation module monitors the feedback data of each rotary encoder in real time and performs velocity mapping and singular configuration avoidance through Jacobian matrix. When the tension difference between any two wire ropes exceeds the safety threshold, the main control unit automatically triggers the tension equalization algorithm to dynamically adjust the torque limit value of each servo drive to prevent the wire ropes from slack or overloaded and breaking, and to ensure the stiffness and motion stability of the parallel traction system. The control system also includes an environmental simulation compensation module, which is linked with the special glass platform and the placement platform 10 for control. The bottom of the special glass platform is integrated with a fluid supply and contact surface characteristic adjustment mechanism. The environmental simulation compensation module dynamically adjusts the fluid medium flow rate or contact surface friction coefficient according to the load conditions and center of gravity position parameters of the object under test, so as to reproduce the boundary conditions of fluid damping and frictional resistance experienced by the hull in water. The environmental simulation compensation module inputs the damping force model as a disturbance feedforward quantity to the position control module, introduces a disturbance observer into the control algorithm, and performs real-time compensation for the positioning lag caused by fluid damping, thereby improving the dynamic tracking accuracy. The main control unit is also equipped with a position holding and adaptive compensation module. When the vision calculation module confirms that the absolute position error is stable within the micron-level tolerance zone, the main control unit outputs a position signal and controls each servo driver to switch to torque holding mode, outputting a holding torque that is balanced with the current load gravity component and residual tension. During the holding period, the vision monitoring unit continuously monitors the position drift in a low-frequency sampling mode. If the position deviation caused by temperature deformation or wire rope creep accumulates to exceed the set threshold, the adaptive compensation module automatically triggers a micro-twist and release rope command to perform closed-loop position reset, achieving long-term high-precision steady-state dwell. The streaming media converter 15 uses a gigabit Ethernet interface and a hardware-level image preprocessing chip to perform distortion correction, brightness equalization, and ROI region cropping on the raw images acquired by the camera 13. After compressing redundant data, it is transmitted to the main control unit via a low-latency industrial Ethernet protocol. The position control module, vision calculation module, and servo driver of the main control unit communicate via EtherCAT or PROFINET IRT real-time Ethernet bus to ensure that the multi-axis synchronous control cycle is ≤1ms and the timestamps of the vision feedback data and control commands are strictly aligned to eliminate the impact of communication jitter on micron-level positioning accuracy. The system is equipped with a dual-redundant safety monitoring architecture. The main control unit compares the encoder data of the primary position feedback unit with the absolute coordinate data of the vision calculation module in real time. When the deviation between the two exceeds the dynamic tolerance range, it is determined that the sensor is faulty or the wire rope is slipping. The emergency stop logic is immediately triggered and the servo drive is locked. The expansion motor 3 is equipped with a mechanical brake device. The control system automatically activates the brake in the event of a power failure or serious fault, and forms a three-level protection through the physical hard limit of the limit frame 9 and the mounting plate 5. The control algorithm has built-in soft limit and acceleration look-ahead planning functions. When approaching the boundary of the test space, it automatically and smoothly decelerates to prevent rigid collision damage to the precision guide roller and the object under test.

[0024] In the above embodiments, the spatial six-degree-of-freedom motion control system maps the six-degree-of-freedom pose matrix of the target position to the length changes and tension distribution coefficients of the six steel wire ropes in real time through the inverse kinematics calculation module in the main control unit. The position control module uses PID algorithm and feedforward compensation algorithm to perform high-speed closed-loop control on the encoder data transmitted by the primary position feedback unit. When the measured object approaches the target position, the vision calculation module automatically increases the feedback priority of the vision monitoring unit. The absolute spatial coordinates are calculated by sub-pixel level edge extraction and feature matching of the image acquired by the camera 13, and fine-tuning compensation commands are generated for low-amplitude high-frequency correction. At the same time, environmental simulation compensation is performed. The module uses the fluid damping force model as the disturbance feedforward input to the position control module and performs real-time compensation through a disturbance observer. The tension balancing algorithm of the six-cable parallel mechanism dynamically adjusts the torque limit value of each servo drive to prevent the wire rope from slack or overload. Finally, it realizes a dual closed-loop servo positioning control architecture with the position loop as the main body and visual feedback as the verification and correction. It effectively solves the technical defects of cumulative error in single encoder feedback and response lag of open-loop vision system. It ensures that the system can still achieve micron-level high-precision positioning and long-term steady-state dwell under complex fluid damping boundary conditions, and significantly improves the control accuracy, response speed and operation stability of six-degree-of-freedom motion simulation. Example 2

[0025] like Figure 1-5 As shown, a spatial six-degree-of-freedom motion simulation device includes: a work box 1 and a support leg 2 disposed at its bottom; The top of the working box 1 is symmetrically distributed with six sets of expansion motors 3. The output end of each set of expansion motors 3 is connected to a wire rope drum. The test space is equipped with a gantry structure consisting of a mounting frame 11 and a connecting frame 12. A double wheel device 7 and a single wheel device 8 are slidably mounted on the mounting frame 11. After the wire rope is drawn out from the drum, it passes through the high-precision guide rollers on the double wheel 7 or the single wheel 8 in sequence, and the end is connected to the object under test through a universal joint; a special glass platform is provided in the middle of the working box 1, and a placement platform 10 is provided above the glass platform to support the object under test. A camera 13 and a fill light 14 are installed at the center of the crossbeam of the connecting frame 12. The optical axis of the camera 13 is perpendicular to the object being measured on the placement platform 10. A matte acrylic plate is fixed on the top of the object being measured. Optical positioning marks are engraved on the surface of the matte acrylic plate. A configurable counterweight module for simulating different load conditions and center of gravity positions is also provided on the side of the work box 1.

[0026] In the above embodiment, the spatial six-degree-of-freedom motion simulation device drives a wire rope drum through six sets of expansion and contraction motors 3 arranged symmetrically around the top of the work box 1. The wire rope passes sequentially around the high-precision guide rollers on the double wheel 7 and single wheel 8 slidably mounted on the mounting frame 11 and then connects to the object under test, forming a statically indeterminate, strongly coupled parallel traction structure. With the help of the camera 13 and supplementary light 14 installed at the center of the crossbeam of the connecting frame 12, real-time image acquisition is performed on the optical positioning markers on the matte acrylic plate on the top of the object under test. At the same time, the specially made glass platform below the object under test simulates fluid damping boundary conditions by adjusting the fluid medium or contact surface characteristics. The counterweight module can be configured to simulate different load conditions and center of gravity positions. Finally, the device achieves accurate reproduction of the six-degree-of-freedom motion of the object under test in three-dimensional space and micron-level positioning test. This effectively solves the technical problems of traditional single-cable traction being unable to achieve complex attitude simulation and insufficient positioning accuracy, and significantly improves the simulation degree and reliability of dynamic behavior testing of floating structures such as ships.

[0027] Working Principle: In use, this invention utilizes six sets of symmetrically arranged expansion and contraction motors 3 around the top of the work box 1 as power sources. Each set of expansion and contraction motors 3 has a wire rope drum connected to its output end, which performs rope winding and unwinding actions under the precise control of a servo drive. After being drawn from the drum, the wire rope sequentially passes over high-precision guide rollers on the double-wheel mechanism 7 and single-wheel mechanism 8 slidably mounted on the mounting frame 11. The spatial layout of the support points of these guide rollers simulates the actual positions of ship winch anchor points. The end of the wire rope is connected to a preset rope-hanging point in the middle of the object being measured via a universal joint, forming a statically indeterminate, strongly coupled parallel traction system. When the six sets of expansion and contraction motors... When motor 3 operates simultaneously according to the preset coordination algorithm, the changes in the length and tension distribution of the six steel wire ropes produce a spatial vector synthesis effect, driving the test object to achieve a composite motion in three-dimensional space along the three translational degrees of freedom (X, Y, Z) and the three rotational degrees of freedom (X, Y, Z). At the same time, the specially designed glass platform set at the bottom of the test object simulates the fluid damping and frictional resistance boundary conditions experienced by the hull in water by adjusting the characteristics of the fluid medium or contact surface. The configurable counterweight module loaded on the side of the test object is used to simulate different load conditions and center of gravity positions, thereby completely reproducing the dynamic behavior characteristics of floating structures such as ships under specific constraints.

[0028] The core working principle of this control system begins with the host computer receiving the target position coordinate parameters set by the user. These parameters typically contain the desired pose information of the measured object in three-dimensional space. After receiving the target pose matrix, the inverse kinematics calculation module in the main control unit performs real-time mathematical mapping calculations using the Jacobian matrix, converting the six-degree-of-freedom pose command in Cartesian space into the required length changes, velocity commands, and tension distribution coefficients for each of the six wire ropes. This inverse kinematics calculation process fully considers the strong coupling characteristics and singular configuration avoidance requirements of the parallel traction system. Subsequently, the position control module outputs the target positions of each axis from the inverse kinematics calculation. The current actual position transmitted by the primary position feedback unit is compared in real time to calculate the position error signal of each axis. The PID control algorithm and feedforward compensation algorithm built into the position control module are comprehensively calculated based on the magnitude, direction and rate of change of the position error. At the same time, the environmental simulation compensation module uses the fluid damping force model as the disturbance feedforward input control loop. The disturbance observer performs real-time compensation for the positioning lag caused by fluid damping, and finally generates the corresponding speed command or torque command. These commands are converted into ±10V analog signals or pulse / bus communication digital commands and output to the corresponding six servo drives through EtherCAT or PROFINET IRT real-time Ethernet bus with a control cycle of ≤1ms, ensuring the accuracy and real-time performance of multi-axis synchronous control.

[0029] After receiving the control command from the main control unit, the servo drive's internal speed loop and torque loop begin to work together, using space vector pulse width modulation technology to generate a three-phase PWM waveform with precisely controllable frequency and amplitude. The permanent magnet synchronous servo motor receives the three-phase current driven by the three-phase PWM waveform and generates precise electromagnetic torque. This electromagnetic torque is amplified by a reducer and transmitted to the wire rope drum, converting rotational motion into linear traction force on the wire rope. The traction force of the six wire ropes, along with the guide roller support points of the double-wheel drive 7 and single-wheel drive 8, forms a statically indeterminate, strongly coupled parallel traction mechanical model, achieving coordinated drive of the six degrees of freedom. During this process, high-resolution rotary encoders installed on the shaft ends of each servo motor serve as primary position feedback units, detecting the angular displacement data of the motor shaft in real time and converting it into wire rope displacement data through the transmission ratio. The linear displacement of the rope and the position information of the measured object are collected, and this position feedback signal is sent back to the main control unit through the industrial real-time bus to form the main feedback closed loop of the system. The tension balancing algorithm of the six-wire parallel mechanism in the main control unit continuously monitors the feedback data of each rotary encoder. When the tension difference between any two wire ropes exceeds the safety threshold, the tension balancing algorithm is automatically triggered to dynamically adjust the torque limit value of each servo drive to prevent the wire rope from slack or overload breakage, and to ensure the stiffness and motion stability of the parallel traction system. At the same time, the dual-redundant safety monitoring architecture configured in the system compares the encoder data with the absolute coordinate data of the subsequent visual calculation module in real time. When the deviation between the two exceeds the dynamic tolerance range, the emergency stop logic is immediately triggered and the mechanical brake device equipped with the retractor motor 3 is activated to form a three-level safety protection system.

[0030] When the object under test approaches the target position under the closed-loop control of the encoder and its movement speed drops to a preset threshold, the system automatically switches the control weight, increases the feedback priority of the visual monitoring unit, and enters the micron-level precise positioning stage. At this time, the camera 13 installed at the center of the crossbeam of the connecting frame 12, under the auxiliary illumination of the supplementary light 14, continuously acquires images of the optical positioning markers engraved on the surface of the matte acrylic plate fixed on the top of the object under test. The streaming media converter 15 uses a gigabit Ethernet interface and a hardware-level image preprocessing chip to perform distortion correction, brightness equalization, and ROI region cropping on the original images acquired by the camera 13. After compressing redundant data, it is transmitted to the main control unit through the low-latency industrial Ethernet protocol. The visual calculation module in the main control unit performs sub-pixel-level edge extraction and feature matching on the image, accurately calculates the absolute spatial coordinates of the center of the marker, and compares the absolute spatial coordinates with the target set position. If the error exceeds the micron-level tolerance, the system will detect the markers. If the speed command is overlaid on the original speed command, the servo motor will perform low-amplitude, high-frequency correction. This visual feedback correction process continues to iterate until the error stabilizes and converges within the tolerance band. When the visual calculation module confirms that the absolute position error is stable within the micron-level tolerance band, the main control unit outputs a position signal and controls each servo driver to switch to torque holding mode, outputting a holding torque that is balanced with the current load gravity component and residual tension. During the holding period, the visual monitoring unit continuously monitors the position drift in a low-frequency sampling mode. If the position deviation caused by temperature deformation or wire rope creep exceeds the set threshold, the adaptive compensation module automatically triggers a micro-twist and release rope command to perform closed-loop position reset, achieving long-term high-precision steady-state dwell. Finally, the entire closed-loop control from coarse positioning to fine positioning is completed, ensuring that the system can still achieve micron-level high-precision positioning and accurate reproduction of programmable motion trajectory under complex fluid damping boundary conditions.

[0031] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A spatial six degree of freedom motion simulation device, characterized by, include: Work box (1) and support feet (2) set at its bottom; The top of the work box (1) is symmetrically distributed with six sets of expansion motors (3). The output end of each set of expansion motors (3) is connected to a wire rope drum. The test space is equipped with a gantry structure consisting of a mounting frame (11) and a connecting frame (12). A double wheel device (7) and a single wheel device (8) are slidably installed on the mounting frame (11). After the wire rope is drawn out from the drum, it passes through the high-precision guide rollers on the double wheel (7) or single wheel (8) in sequence, and the end is connected to the object to be measured through a universal joint; a special glass platform is provided in the middle of the work box (1), and a placement platform (10) is provided above the glass platform, which is used to support the object to be measured. A camera (13) and a fill light (14) are installed at the center of the crossbeam of the connecting frame (12). The optical axis of the camera (13) is perpendicular to the object to be tested on the placement platform (10). A matte acrylic plate is fixed on the top of the object to be tested. Optical positioning marks are engraved on the surface of the matte acrylic plate. A configurable counterweight module for simulating different load conditions and center of gravity positions is also provided on the side of the work box (1).

2. The spatial six-degree-of-freedom motion control system according to claim 1, characterized in that, include: Main control unit, drive execution unit, primary position feedback unit and visual monitoring unit; The main control unit communicates with the drive execution unit through an industrial real-time bus. The drive execution unit includes a servo driver and a permanent magnet synchronous servo motor that are electrically connected to the six sets of zoom motors (3) in a one-to-one correspondence. The primary position feedback unit is composed of a high-resolution rotary encoder installed on the shaft end of each servo motor, which is used to collect the angular displacement of the motor in real time and convert it into the linear displacement of the wire rope through the transmission ratio. The visual monitoring unit includes the camera (13), the fill light (14), and the streaming media converter (15). The streaming media converter (15) transmits the image data collected by the camera (13) to the main control unit in real time. The main control unit integrates a position control module and a visual calculation module to construct a closed-loop servo positioning control architecture with position loop as the main factor and visual feedback as the verification and correction.

3. A spatial six-degree-of-freedom motion control system according to claim 2, characterized in that, The position control module of the main control unit is configured to execute the following control logic: receive the target position coordinate parameters set by the host computer and convert them into a position setpoint that the control system can recognize; acquire the current actual position transmitted by the primary position feedback unit in real time and calculate the position error between the position setpoint and the current actual position; perform real-time calculation based on the magnitude and direction of the position error using a preset PID control algorithm and feedforward compensation algorithm to generate corresponding speed commands or torque commands; convert the speed commands or torque commands into ±10V analog signals or pulse / bus communication digital commands and output them to the corresponding servo driver.

4. A spatial six-degree-of-freedom motion control system according to claim 3, characterized in that, After receiving the control command output by the main control unit, the servo driver's internal speed loop and torque loop work together to generate a three-phase PWM waveform with precise controllable frequency and amplitude using space vector pulse width modulation technology. The permanent magnet synchronous servo motor receives the three-phase current driven by the three-phase PWM waveform and generates precise electromagnetic torque. The electromagnetic torque is amplified by the reducer and then transmitted to the wire rope drum, converting the rotational motion into the linear traction force of the wire rope, driving the object under test to move along a preset trajectory in three-dimensional space. The traction force of the wire rope and the guide roller support points of the double wheel (7) and single wheel (8) form a statically indeterminate strongly coupled parallel traction mechanical model, realizing coordinated driving of six degrees of freedom attitude.

5. A spatial six-degree-of-freedom motion control system according to claim 2, characterized in that, The visual calculation module is configured to execute micron-level precision positioning logic: when the primary position feedback unit detects that the object under test is approaching the target position and the movement speed drops to a preset threshold, the main control unit automatically switches the control weight and increases the feedback priority of the visual monitoring unit; the camera (13) continuously collects images of optical positioning markers on the matte acrylic plate on the top of the object under the auxiliary illumination of the supplementary light (14); the visual calculation module performs sub-pixel-level edge extraction and feature matching on the image and calculates the absolute spatial coordinates of the center of the marker; the absolute spatial coordinates are compared with the target set position, and if the error exceeds the micron-level tolerance band, a fine-tuning compensation command is generated and superimposed on the original speed command to drive the servo motor to perform low-amplitude high-frequency correction until the error is stably converged within the tolerance band.

6. A spatial six-degree-of-freedom motion control system according to claim 2, characterized in that, The main control unit is embedded with a six-wire parallel mechanism inverse kinematics calculation module, which maps the six-degree-of-freedom pose matrix of the target position to the length changes and tension distribution coefficients of the six wire ropes. The inverse kinematics calculation module monitors the feedback data of each rotary encoder in real time and performs velocity mapping and singular configuration avoidance through Jacobian matrix. When the tension difference between any two wire ropes exceeds the safety threshold, the main control unit automatically triggers the tension equalization algorithm to dynamically adjust the torque limit value of each servo drive to prevent the wire ropes from slack or overloaded and breaking, and to ensure the stiffness and motion stability of the parallel traction system.

7. A spatial six-degree-of-freedom motion control system according to claim 2, characterized in that, The control system also includes an environmental simulation compensation module, which is linked to the special glass platform and the placement platform (10) for control. The bottom of the special glass platform is integrated with a fluid supply and contact surface characteristic adjustment mechanism. The environmental simulation compensation module dynamically adjusts the fluid medium flow rate or contact surface friction coefficient according to the load conditions and center of gravity position parameters of the object under test, so as to reproduce the fluid damping and friction resistance boundary conditions of the hull in water. The environmental simulation compensation module inputs the damping force model as a disturbance feedforward quantity to the position control module, introduces a disturbance observer in the control algorithm, and performs real-time compensation for the positioning lag caused by fluid damping, thereby improving the dynamic tracking accuracy.

8. A spatial six-degree-of-freedom motion control system according to claim 5, characterized in that, The main control unit is also equipped with a position holding and adaptive compensation module. When the vision calculation module confirms that the absolute position error is stable within the micron-level tolerance zone, the main control unit outputs a position signal and controls each servo driver to switch to torque holding mode, outputting a holding torque that is balanced with the current load gravity component and residual tension. During the holding period, the vision monitoring unit continuously monitors the position drift in a low-frequency sampling mode. If the position deviation caused by temperature deformation or wire rope creep accumulates to exceed a set threshold, the adaptive compensation module automatically triggers a micro-twist and release rope command to perform closed-loop position reset, achieving long-term high-precision steady-state dwell.

9. A spatial six-degree-of-freedom motion control system according to claim 2, characterized in that, The streaming media converter (15) uses a gigabit Ethernet interface and a hardware-level image preprocessing chip to perform distortion correction, brightness equalization and ROI region cropping on the original image acquired by the camera (13). After compressing redundant data, it is transmitted to the main control unit through the low-latency industrial Ethernet protocol. The position control module, vision calculation module and servo driver of the main control unit communicate with each other through EtherCAT or PROFINET IRT real-time Ethernet bus to ensure that the multi-axis synchronous control cycle is ≤1ms, and the timestamps of the visual feedback data and control commands are strictly aligned to eliminate the impact of communication jitter on the micron-level positioning accuracy.

10. A spatial six-degree-of-freedom motion control system according to claim 2, characterized in that, The system is configured with a dual-redundant safety monitoring architecture; the main control unit compares the encoder data of the primary position feedback unit with the absolute coordinate data of the vision calculation module in real time. When the deviation between the two exceeds the dynamic tolerance range, it is determined that the sensor is faulty or the wire rope is slipping, and the emergency stop logic is immediately triggered and the servo drive is locked; the expansion motor (3) is equipped with a mechanical brake device. The control system automatically activates the brake in the event of power failure or serious fault, and forms a three-level protection through the physical hard limit of the limit frame (9) and the mounting plate (5); the control algorithm has built-in soft limit and acceleration look-ahead planning functions, and automatically and smoothly decelerates when approaching the boundary of the test space to prevent rigid collision damage to the precision guide roller and the object under test.

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