Mechanical arm tail end clamp system and control device and control method thereof

Abstract

The invention provides a mechanical arm tail end clamp system and a control method thereof. The mechanical arm tail end clamp system comprises a structure supporting frame; the combined connecting piece is located in the structural supporting frame and can linearly move relative to the structural supporting frame; the transmission control device comprises a double-shaft stepping motor, a linear guide rail, two ball screws, two moving nuts and a linear moving sliding block, the double-shaft stepping motor and the linear guide rail are located in the structure supporting frame, the ball screws are sleeved with the two moving nuts, the two moving nuts are fixedly connected with the combined connecting pieces on the two sides respectively, and the linear moving sliding block is fixedly connected with the combined connecting pieces; the end of the clamp arm is hinged to the combined connecting piece, and the combined connecting piece moves linearly to drive the head of the clamp arm structure to move transversely. The stroke track frame is fixed below the structure supporting frame, and a sliding limiting piece is arranged on the inner side of the stroke track frame and connected with the clamp arm in a sliding mode. According to the mechanical arm tail end clamp system, the model selection requirement of the lead screw can be lowered, and therefore the stability of the clamp is improved while the manufacturing cost is reduced, and the service life of the clamp is prolonged.

Description

Technical Field

[0001] The present invention relates to the technical field of robotic arms, and particularly to an end-effector fixture system of a robotic arm and a control method therefor. Background Art

[0002] Robotic arms are widely used in various links of industrial production. As an important part of them, the working performance of the end-effector directly affects the working efficiency and stability of the robotic arm. When facing parts with different shapes, sizes and weights, the traditional fixture structure has disadvantages such as non-adjustable speed, low strength and poor accuracy. At the same time, the control of stepper motors usually depends on the cooperation of dedicated controllers and external signals. The control systems of such methods are complex, costly and inflexible to adjust. With the development of manufacturing production processes and the increase in labor costs, optimizing the end-effector of the robotic arm and the corresponding control method is an inevitable choice for the sustainable development of future manufacturing.

[0003] While traditional end-effectors use ball screws as the transmission structure, they also require the screw to bear the load when clamping workpieces. This design requires the selection of screws with higher stiffness and load-bearing capacity, resulting in an increase in manufacturing costs and maintenance costs. At the same time, during long-term use, the force-bearing condition of the ball screw may affect its service life and transmission accuracy. In addition, existing motor or pneumatic-driven end-effectors usually adopt a fixed input mode, resulting in difficult precise control of the movement speed of the fixture arm and the clamping size of the fixture, affecting the stability and accuracy of the operation. Summary of the Invention

[0004] The main purpose of the present invention is to provide an end-effector fixture system of a robotic arm, a control device and a control method therefor, aiming to reduce the selection requirements of the screw, thereby reducing manufacturing costs while improving the stability and service life of the fixture.

[0005] To achieve the above object, the present invention provides an end-effector fixture system of a robotic arm, including:

[0006] A structural support frame;

[0007] A combined connecting member, located inside the structural support frame and linearly movable relative thereto;

[0008] A transmission and control device, including a dual-axis stepper motor and a linear guide rail located inside the structural support frame, two ball screws fixedly connected to the output shaft of the dual-axis stepper motor, two moving nuts sleeved on the ball screws, and a linear motion slider installed on the linear guide rail. The two moving nuts are respectively fixedly connected to the combined connecting members on both sides to drive the combined connecting members to move linearly, and the linear motion slider is fixedly connected to the combined connecting member to guide and bear the load for the linear movement of the combined connecting member;

[0009] A fixture arm, whose end is hinged to a combined connector, and the head of the fixture arm structure is driven to move horizontally by the linear movement of the combined connector;

[0010] A stroke track frame, fixed below the structure support frame, and a sliding limit member is arranged inside it and slidably connected to the fixture arm.

[0011] Preferably, linear guide rails are arranged at both the top end and the bottom end of the double-axis stepper motor, and linear motion sliders are fixed at both the top and the bottom of the combined connector; the control device further includes a housing for accommodating the double-axis stepper motor and the linear guide rails, and a brake installed at the end of the ball screw. The moving nut is threadedly connected to the ball screw. When the output shaft of the double-axis stepper motor rotates, it drives the ball screw to rotate and then drives the moving nut to move linearly.

[0012] Preferably, the housing includes a top plate and side plates located on both sides of the top plate. The structure support frame includes a front plate, a rear plate, and a top support plate connecting the front plate and the rear plate. The top plate is fixed below the top support plate, and both ends of the two linear guide rails are respectively fixed to the side plates. The double-axis stepper motor is located between the two linear guide rails.

[0013] Preferably, the combined connector includes a moving block located in the middle and fixedly connected to the moving nut, two H-shaped connectors fixed on the front and rear sides of the moving block, an I-shaped connecting flange fixed on the outside of the H-shaped connector, a rotating shaft fixed at the end of the connecting flange, and a rotating shaft top cover installed at the end of the rotating shaft and rotatably connected to it. The end of the fixture arm is sleeved outside the rotating shaft and fixedly connected to the rotating shaft top cover. Linear motion sliders are fixed on both the upper and lower sides of the moving block.

[0014] Preferably, the mechanical arm end fixture system further includes a top connecting flange fixed on the top of the structure support frame and an end clamping block fixed on the clamping end of the fixture arm; the sliding limit member includes a rolling bearing installed on the fixture arm, and a chute for accommodating the rolling bearing for sliding is opened on the stroke track frame.

[0015] The present invention also proposes a control device based on the above mechanical arm end fixture system, including:

[0016] A PLC main control unit, used to receive the control signal input by the user and generate corresponding output signals according to the control logic;

[0017] A motor driver, used to receive the stepping pulse signal controlled by the PLC main control unit and drive the motor to rotate precisely;

[0018] An external control device, used to input motion commands and adjust the working characteristics of the fixture;

[0019] A load detection system, used to detect the load of the double-axis stepper motor and the touch situation at the end of the fixture in real time;

[0020] A feedback system for limiting the number of rotation cycles and the moving distance of a biaxial stepper motor;

[0021] A power management system for supplying power to the motor driver and the PLC main control unit to ensure the normal operation of each component;

[0022] A protection module for preventing abnormal operation of the biaxial stepper motor.

[0023] Preferably, the PLC main control unit controls the motor driver in a PTO control mode. The PTO control mode controls the movement speed, stroke, and clamping size of the fixture arm by changing the number of pulses and the frequency of the input pulses of the biaxial stepper motor.

[0024] The present invention also provides a control method for a control device of a mechanical arm end fixture system based on the above, including forward rotation control and reverse rotation control.

[0025] The forward rotation control includes: after the PLC main control unit receives the forward rotation command information, it generates a forward or reverse pulse signal, and the pulse frequency gradually decreases from the initial value, and the biaxial stepper motor gradually accelerates to the set speed and then gradually decelerates.

[0026] The reverse rotation control includes: after the PLC main control unit receives the reverse rotation command signal, it generates a reverse pulse signal, and the pulse frequency gradually increases from the initial value, and the motor gradually accelerates and stops after completing the specified number of rotation cycles.

[0027] Preferably, it further includes a flexible clamping control method, and its steps include:

[0028] The PLC main control unit controls the biaxial stepper motor to output a forward rotation pulse signal to drive the fixture to perform a clamping action;

[0029] During the forward rotation of the output shaft of the biaxial stepper motor, the PLC main control unit real-time collects sensor signals related to the load and the end touch;

[0030] When it is detected that the load signal reaches the set threshold, or the force of the end touch reaches a certain value, the PLC main control unit immediately stops outputting the pulse signal;

[0031] The PLC main control unit records the pulse count value at the stop and calculates the actual number of rotation cycles as the determination basis for the fixture closing size;

[0032] The PLC main control unit controls the brake at the end of the lead screw to work to ensure that the lead screw no longer rotates after the fixture is clamped.

[0033] Preferably, it further includes the following steps:

[0034] Use a load detection system to monitor the load condition of the dual-axis stepper motor in real time. When the load exceeds the set threshold, the PLC automatically stops the pulse output of the dual-axis stepper motor to stop its operation.

[0035] Transmit the magnitude of the clamping force of the fixture through the force sensor at the end of the fixture arm. If the clamping force exceeds the set value, the PLC main control unit automatically stops the stepper pulse output, and the main control unit controls the brake to start braking.

[0036] The fixture system at the end of the robotic arm proposed by the present invention has the following beneficial effects:

[0037] 1. By installing a linear guide structure, the load is borne by the linear guide, and the ball screw is only used to provide the transmission function. The screw no longer directly bears the load, reducing its load requirement. Instead, the linear guide bears the force of the machine fixture, making the selection of the screw more flexible. Even a smaller specification screw can be selected, thereby reducing the overall manufacturing cost.

[0038] 2. Since the linear guide structure itself has a high load-bearing capacity and stiffness, it can effectively disperse the load, and the ball screw is only responsible for transmission, avoiding wear and deformation caused by excessive load. This enables the fixture to maintain a high positioning accuracy during long-term operation, thereby improving the stability and service life of the entire system. After long-term operation of traditional end fixtures, the ball screw is prone to replacement due to load fatigue. The fixture system at the end of this robotic arm can effectively reduce the wear of the screw, extend the maintenance cycle, and reduce the maintenance cost.

[0039] 3. By using a stepper motor and combining it with the PLC pulse control method, the movement speed of the fixture arm and the clamping size of the fixture can be flexibly adjusted, improving the accuracy and efficiency of automated production.

[0040] 4. The fixture system at the end of this robotic arm has the advantages of simple structure, stable and reliable operation, and easy implementation. Brief Description of the Drawings

[0041] Figure 1 It is a schematic structural diagram of the fixture system at the end of the robotic arm of the present invention;

[0042] Figure 2 It is a schematic structural diagram of the fixture arm in the fixture system at the end of the robotic arm of the present invention;

[0043] Figure 3 It is a schematic structural diagram of the combined connector in the fixture system at the end of the robotic arm of the present invention;

[0044] Figure 4 It is a schematic partial structural diagram of the fixture system at the end of the robotic arm of the present invention;

[0045] Figure 5It is a structural block diagram of the control device for the end-effector system of the robotic arm of the present invention;

[0046] Figure 6 It is the overall control flowchart of the input pulses of the stepper motor in the control device for the end-effector system of the robotic arm of the present invention;

[0047] Figure 7 It is the displacement-time graph of the gripper arm in the control device for the end-effector system of the robotic arm of the present invention;

[0048] Figure 8 It is the velocity-time graph of the gripper arm in the control device for the end-effector system of the robotic arm of the present invention.

[0049] In the figure, 1 - top connection flange; 2 - structural support frame; 3 - combined connecting piece, 31 - rotating shaft top cover, 32 - top cover rolling bearing, 33 - rotating shaft, 34 - I-shaped connecting flange, 35 - moving block, 36 - moving nut, 37 - H-shaped connecting piece, 38 - rotating shaft rolling bearing; 4 - transmission and control device, 401 - side plate, 402 - ball screw, 403 - linear guide rail, 404 - top plate, 405 - linear guide rail slider, 406 - motor rolling bearing, 407 - motor mounting housing, 408 - dual-axis stepper motor, 409 - coupling, 410 - screw rolling bearing, 411 - screw end rolling bearing, 412 - brake; 5 - gripper arm, 51 - motion bearing, 52 - clamping arm; 6 - stroke track frame; 7 - end clamping block.

[0050] The realization, functional features and advantages of the object of the present invention will be further described in conjunction with the embodiments with reference to the accompanying drawings. Detailed implementation manners

[0051] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0052] It should be noted that in the description of the present invention, the orientation or positional relationship indicated by the terms "lateral", "longitudinal", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0053] The present invention provides an end-effector system for a robotic arm.

[0054] Refer to Figures 1 to 4, in this preferred embodiment, a robotic arm end effector system includes:

[0055] A structural support frame 2;

[0056] A combined connecting member 3, located inside the structural support frame 2 and linearly movable relative thereto;

[0057] A transmission and control device 4, including a two-axis stepper motor 408 and a linear guide rail 403 located inside the structural support frame 2, two ball screws 402 fixedly connected to the output shaft of the two-axis stepper motor 408, two moving nuts 36 sleeved on the ball screws 402, and a linear motion slider mounted on the linear guide rail 403. The two moving nuts 36 are respectively fixedly connected to the combined connecting members 3 on both sides to drive the combined connecting members 3 to move linearly, and the linear motion slider is fixedly connected to the combined connecting members 3 to guide the linear movement of the combined connecting members 3 and carry the load;

[0058] A clamp arm 5, whose end is hinged to the combined connecting member 3, and drives the lateral movement of the head of the clamp arm 5 structure through the linear movement of the combined connecting member 3;

[0059] A stroke trajectory frame 6, fixed below the structural support frame 2 and having sliding limit members provided on its inner side for sliding connection with the clamp arm 5.

[0060] The clamp arm 5 includes two clamping arms 52 arranged oppositely. Further, linear guide rails 403 are provided at both the top and bottom of the two-axis stepper motor 408, and linear motion sliders are fixedly installed at both the top and bottom of the combined connecting member 3.

[0061] In this embodiment, by providing linear guide rails 403 at both the top and bottom of the two-axis stepper motor 408, on the one hand, the load on the screw is greatly reduced, and on the other hand, the combined connecting member 3 is stably guided from both the upper and lower ends to ensure its smooth operation during linear movement, thereby ensuring the clamping accuracy.

[0062] Specifically, in this embodiment, the transmission and control device 4 further includes a housing for accommodating the two-axis stepper motor 408 and the linear guide rail 403, and a brake 412 installed at the end of the ball screw 402. The moving nut 36 is threadedly connected to the ball screw 402. When the output shaft of the two-axis stepper motor 408 rotates, it drives the ball screw 402 to rotate and then drives the moving nut 36 to move linearly. The central axis plane of the two-axis stepper motor 408 coincides with the central axis plane of the housing of the transmission and control device 4, and motor rolling bearings 406 are respectively fixedly installed on both sides of the output shaft, and then connected to the coupling 409.

[0063] The input shaft of the ball screw 402 is connected to the coupling 409 and is in interference fit with the screw rolling bearing 410. The other side of the ball screw 402 is in interference fit with the screw end rolling bearing 411 and is equipped with a brake 412.

[0064] Referring to Figure 4 , in this embodiment, the housing includes a top plate 404 and side plates 401 on both sides of the top plate 404. The structural support frame 2 includes a front plate, a rear plate, and a top support plate connecting the front plate and the rear plate. The top plate 404 is fixed below the top support plate. The two ends of the two linear guide rails 403 are respectively fixedly connected to the two side plates 401, and the dual-axis stepper motor 408 is located between the two linear guide rails 403.

[0065] Referring to Figure 3 , specifically, the combined connecting piece 3 includes a moving block 35 located in the middle and fixedly connected to the moving nut 36, two H-shaped connecting pieces 37 fixed on the front and rear sides of the moving block 35, an I-shaped connecting flange 34 fixed on the outside of the H-shaped connecting piece 37, a rotating shaft 33 fixed at the end of the I-shaped connecting flange 34, and a rotating shaft 33 top cover 31 installed at the end of the rotating shaft 33 and rotatably connected to it. The end of the fixture arm 5 is sleeved outside the rotating shaft 33 and fixedly connected to the rotating shaft 33 top cover 31. Linear motion sliders are fixed on both the upper and lower sides of the moving block 35. The central axis plane of the moving nut 36 coincides with the central axis plane of the moving block 35, and the two are fixedly connected by bolts.

[0066] The H-shaped connecting pieces 37 are respectively processed with threaded holes for the moving block 35, the linear motion slider, and the I-shaped connecting flange 34, and the connection methods are bolt connection, screw connection, and bolt connection in sequence.

[0067] The I-shaped connecting flange 34 and the rotating shaft 33 are bolt-connected. A counterbore is provided on one side of the I-shaped connecting flange 34 to ensure the fixation of the rotating shaft 33 and prevent it from rotating with the fixture arm 5. During actual installation, after passing the fixture arm 5 through the rotating shaft 33, it is then fixed to the rotating shaft 33 top cover 31 with screws. Top cover rolling bearings 32 and rotating shaft rolling bearings 38 are respectively installed on both sides of the rotating shaft 33 to ensure that the rotating shaft 33 top cover 31 can rotate with the fixture arm 5.

[0068] When the dual-axis stepper motor 408 is started, it drives the ball screw 402 to rotate through the coupling 409 and the motor rolling bearing 406. Since the moving nut 36 and the ball screw 402 are thread-connected, the circular motion of the ball screw 402 itself is converted into the linear motion of the moving nut 36, and through the combined connecting piece 3, it drives the linear slider to do linear motion.

[0069] Furthermore, the end-effector fixture system of the robotic arm further includes a top connection flange 1 fixed to the top of the structural support frame 2 and an end clamping block fixed to the clamping end of the fixture arm 5. The top connection flange 1 is connected to the structural support frame 2 by screws and bolts. Threaded holes are distributed on the upper and lower surfaces of the structural support frame 2 for installing the housing of the transmission and control device 4 and the linear guide 403 respectively.

[0070] The sliding limit member includes a motion bearing 51 installed on the fixture arm 5, and a sliding groove for accommodating the motion bearing 51 for sliding is provided on the travel track frame 6. The upper part of the travel track frame 6 is riveted to the structural support frame 2.

[0071] The working process of the end-effector fixture system of the robotic arm is as follows:

[0072] When the combined connecting member 3 moves with the moving nut 36, it will drive the two clamping arms 52 to move along the inner groove of the travel track frame 6, so that the fixture completes the contraction and expansion movements.

[0073] When the two moving nuts 36 move in the direction away from the double-axis stepper motor 408, the distance between the upper part of the clamping arm 52 and the travel track frame 6 becomes larger, and the middle part of the clamping arm 52 moves upward along the inner groove. At this time, the two end clamping blocks 7 approach each other, and the fixture completes the clamping action.

[0074] When the two moving nuts 36 move in the direction close to the double-axis stepper motor 408, the distance between the upper part of the clamping arm 52 and the travel track frame 6 becomes smaller, and the middle part of the clamping arm 52 moves downward along the inner groove. At this time, the two end clamping blocks 7 move away from each other, and the fixture completes the expansion action.

[0075] The end-effector fixture system proposed by the present invention has the following beneficial effects:

[0076] 1. By installing the linear guide 403 structure, the load is borne by the linear guide 403, and the ball screw 402 is only used to provide the transmission function. The screw no longer directly bears the load, reducing its load requirement. Instead, the linear guide 403 bears the force of the machine fixture, making the selection of the screw more flexible. Even a smaller specification screw can be selected, thus reducing the overall manufacturing cost;

[0077] 2. Since the linear guide 403 structure itself has a high load-bearing capacity and stiffness, it can effectively disperse the load, and the ball screw 402 is only responsible for transmission, avoiding wear and deformation caused by excessive load. This enables the fixture to maintain a high positioning accuracy during long-term operation, thereby improving the stability and service life of the entire system. In the case of traditional end-effectors, the ball screw 402 is prone to replacement due to load fatigue after long-term operation. The end-effector fixture system of this robotic arm can effectively reduce the wear of the screw, extend the maintenance cycle, and reduce the maintenance cost;

[0078] 3. By adopting a stepper motor and combining it with the PLC pulse control method, the movement speed of the fixture arm 5 and the fixture clamping size can be flexibly adjusted, improving the accuracy and efficiency of automated production;

[0079] 4. The fixture system at the end of this robotic arm has the advantages of simple structure, stable and reliable operation, and easy implementation.

[0080] The present invention further proposes a control device for a fixture system at the end of a robotic arm.

[0081] Referring to Figure 5 , in this preferred embodiment, a control device for a fixture system at the end of a robotic arm based on the above includes:

[0082] A PLC main control unit, which is used to receive the control signals input by the user and generate corresponding output signals according to the control logic;

[0083] A motor driver, electrically connected to the PLC main control unit, which is used to receive the stepping pulse signal controlled by the PLC main control unit and drive the dual-axis stepper motor 408 to rotate precisely;

[0084] An external control device, electrically connected to the PLC main control unit, which is used to input motion commands, adjust the working characteristics of the fixture, and convert them into corresponding control signals and send them to the PLC main control unit;

[0085] A load detection system, electrically connected to the PLC main control unit, which is used to detect the load of the dual-axis stepper motor 408 and the touch situation at the end of the fixture in real time;

[0086] A feedback system, electrically connected to the PLC main control unit, which is used to limit the number of rotation turns and the motion distance of the dual-axis stepper motor 408;

[0087] A power management system, electrically connected to the PLC main control unit and the motor driver, which is used to supply power to the motor driver and the PLC main control unit to ensure the normal operation of each component;

[0088] A protection module, electrically connected to the PLC main control unit, which is used to prevent the dual-axis stepper motor 408 from having abnormal operation.

[0089] The PLC main control unit receives the control signals input by the user and generates corresponding output signals according to the control logic. The PLC main control unit controls the motor driver by using the PTO control method. The PTO control method controls the movement speed, stroke, and fixture clamping size of the fixture arm 5 by changing the number of pulses and the frequency of the input pulses of the dual-axis stepper motor 408.

[0090] Specifically, the external control device includes a variable speed control device, a direction control button, and a human-machine interface.

[0091] A variable speed control device for adjusting the speed of a motor, which transmits signals to the PLC main control unit through an analog input (AI). The PLC main control unit adjusts the pulse frequency of the two-axis stepper motor 408 according to the signals to change the speed of the motor;

[0092] A direction control button for manually controlling the forward or reverse rotation of the two-axis stepper motor 408;

[0093] A human-machine interface, which inputs motion commands through a touch screen or a computer interface. The PLC main control unit receives the input parameters and controls the two-axis stepper motor 408 according to the output;

[0094] The load detection system includes: a current sensor, a torque sensor, and a force sensor;

[0095] The current sensor, which can be a Hall sensor, is used to monitor the current of the motor driver;

[0096] The torque sensor is installed on the output shaft of the two-axis stepper motor 408 to monitor the output torque of the two-axis stepper motor 408 in real time for accurate load judgment;

[0097] The force sensor is installed on the fixture arm 5 to monitor the force at the end of the fixture arm 5 in real time. After receiving a certain amount of force, it outputs a control signal to the PLC main control unit to control the magnitude of the clamping force.

[0098] The feedback system includes a position sensor and a limit switch;

[0099] The position sensor helps the PLC main control unit judge the actual movement progress of the two-axis stepper motor 408 to ensure that it stops after rotating a specified number of turns, and is used to feedback the position information or the number of completed movement turns of the two-axis stepper motor 408;

[0100] The limit switch ensures that the two-axis stepper motor 408 operates within a specified range, physically limits the movement range during the operation of the two-axis stepper motor 408, and prevents the two-axis stepper motor 408 from over-running or being damaged.

[0101] The protection module includes a temperature sensor and an overload protection module;

[0102] The temperature sensor is used to monitor the temperatures of the two-axis stepper motor 408 and the power supply module to avoid hardware failures caused by overheating;

[0103] The overload protection module automatically triggers a protection program to cut off the power supply when the PLC main control unit or the motor driver is overloaded or abnormal, preventing equipment damage.

[0104] Specifically, during the forward and reverse control process of the dual-axis stepper motor 408, the PLC determines the rotation direction of the dual-axis stepper motor 408 based on the external input signal and switches the direction of the step pulse output in the control logic.

[0105] When receiving the forward rotation command signal, the PLC main control unit controls the start of the dual-axis stepper motor 408 and sets the initial pulse frequency to F0. Then, according to the set acceleration parameter a1 and deceleration parameter a2, it controls the frequency change through the following formula (1) to enable the dual-axis stepper motor 408 to accelerate first and then decelerate:

[0106]

[0107] where F1 is the frequency at the end of the acceleration stage, t1 is the acceleration duration, and t2 is the duration of the entire forward rotation process.

[0108] During the forward rotation process of the dual-axis stepper motor 408, by integrating the load detection module and the end detection module, the stop condition is dynamically determined during the forward rotation process of the dual-axis stepper motor 408, as Figure 6 shown, thereby indirectly controlling the contraction distance of the clamping arm 52 to achieve flexible adaptation to workpieces of different sizes.

[0109] During the process of controlling the contraction of the fixture arm 5, the PLC main control unit simultaneously collects the current feedback signal I(t) of the drive circuit of the dual-axis stepper motor 408 and the touch force sensor F(t) installed inside the end clamping block 7;

[0110] The PLC main control unit determines whether the stop condition is met. If I(t) ≥ I th , and t ≥ Δt safe , that is, both the load and the duration exceed the set thresholds; if F(t) ≥ F th , that is, the clamping force exceeds the set threshold;

[0111] If any of the above conditions is met, the PLC main control unit immediately terminates the pulse output, the dual-axis stepper motor 408 stops, and the brake 4124 starts to work, and the clamping arm 52 remains in the current position without moving;

[0112] The PLC main control unit reads the current pulse count P act , and based on the number of pulses P rev required for each revolution of the dual-axis stepper motor 408, calculates the actual number of revolutions:

[0113] N act =P act / P rev . (2)

[0114] The number of revolutions N actThe contraction distance of the corresponding clamping arm 52 is used as the current clamping size result to display the actual clamping distance and identify the part specifications in the HMI;

[0115] When receiving the reverse command signal, the PLC main control unit controls the operation of the two-axis stepping motor 408 in reverse, sets the initial frequency to F0′, and then gradually increases the control frequency until it reaches the maximum frequency F2, and stops output after the two-axis stepping motor 408 reaches the set number of turns N:

[0116] f (t) = F0′ + a3·t, 0 < t < t r (3)

[0117] where a3 is the reverse acceleration, and t r is the time required to complete N turns, which can be obtained by converting the step angle and the number of pulses of the two-axis stepping motor 408.

[0118] Let the step angle of the two-axis stepping motor 408 be θ s , then the number of pulses required per turn is:

[0119]

[0120] Therefore, the total number of pulses required for N turns is:

[0121] P total = N·P rev (5)

[0122] The PLC main control unit internally records the pulse output in real time through a pulse counter. When the total number of pulses reaches P total , it automatically stops, and at the same time the brake 412 starts to work;

[0123] During the forward and reverse rotation of the two-axis stepping motor 408, the PLC main control unit obtains the speed setting value v set by receiving an external speed control signal, and maps it to the corresponding pulse frequency range:

[0124]

[0125] where f min is the minimum operating frequency of the two-axis stepping motor 408; f max is the maximum frequency allowed by the two-axis stepping motor 408; v set is the input voltage; v max , v min are the minimum and maximum value ranges of the analog input;

[0126] The PLC master control unit controls the interval of each pulse through high-speed timing interrupts, and converts analog signals into frequency control sequences using step functions or linear interpolation functions, thereby achieving dynamic frequency adjustment.

[0127] The PLC master control unit executes the logic in a cyclic manner in periodic tasks or interrupt tasks as shown in the appendix Figure 6 The displacement and velocity curves of the clamping arm 52 with respect to time are as shown in the appendix Figure 7 and Figure 8 as shown.

[0128] The control device proposed by the present invention uses the PTO output pulse of the PLC master control unit, and can accurately control the movement speed and clamping size of the fixture arm 5 through methods such as acceleration and deceleration control and conditional triggering. By adjusting the pulse frequency, the output speed of the dual-axis stepper motor 408 can be accurately controlled for different working conditions, improving the usage efficiency of the fixture; according to the size of different workpieces, different pulse numbers are set to adjust the clamping margin of the fixture arm 5, realizing flexible adjustment of the clamping size and flexible automation control.

[0129] The pulse frequency is input to the dual-axis stepper motor 408 to adjust the movement speed of the fixture arm 5; the pulse length is input to the dual-axis stepper motor 408 to adjust the clamping margin of the fixture arm 5. The dual-axis stepper motor 408 outputs different speeds at different working stages. The increasing or decreasing change of the pulse frequency can smoothly control the acceleration and deceleration movements of the dual-axis stepper motor 408, avoiding structural impact damage caused by sudden acceleration changes. While improving the handling efficiency of the manipulator, it can effectively reduce the impact load on the structure caused by stalling to meet the actual working requirements of automobile parts assembly.

[0130] The present invention further proposes a control method for a control device of a fixture system at the end of a robotic arm.

[0131] In this preferred embodiment, a control method for a control device of a fixture system at the end of a robotic arm based on the above includes forward rotation control and reverse rotation control.

[0132] The forward rotation control includes: after the PLC master control unit receives the forward rotation command information, it generates a forward or reverse pulse signal, the pulse frequency gradually decreases from the initial value, and the dual-axis stepper motor 408 gradually accelerates to the set speed and then gradually decelerates.

[0133] The reverse rotation control includes: after the PLC master control unit receives the reverse rotation command signal, it generates a reverse pulse signal, the pulse frequency gradually increases from the initial value, and the motor gradually accelerates and stops after completing the specified number of turns.

[0134] Furthermore, the control method for a control device of a fixture system at the end of a robotic arm includes a flexible clamping control method, and its steps include:

[0135] Step S10: The PLC main control unit controls the dual-axis stepper motor 408 to output a forward rotation pulse signal, driving the fixture to perform a clamping action.

[0136] Step S20: During the forward rotation of the output shaft of the dual-axis stepper motor 408, the PLC main control unit real-time collects sensor signals related to the load and the touch of the end.

[0137] Step S30: When it is detected that the load signal reaches the set threshold or the force of the end touch reaches a certain value, the PLC main control unit immediately stops outputting the pulse signal.

[0138] Step S40: The PLC main control unit records the pulse count value at the stop and calculates the actual number of rotation turns, which is used as the judgment basis for the closing dimension of the fixture.

[0139] Step S50: The PLC main control unit controls the brake 412 at the end of the lead screw to work, ensuring that the lead screw stops rotating after the fixture is clamped.

[0140] Furthermore, the control method of the control device of the end fixture system of the robotic arm further includes the following steps:

[0141] Use the load detection system to monitor the load condition of the dual-axis stepper motor 408 in real time. When the load exceeds the set threshold, the PLC automatically stops the pulse output of the dual-axis stepper motor 408 to stop the operation of the dual-axis stepper motor 408.

[0142] Transmit the magnitude of the clamping force of the fixture through the force sensor at the end of the fixture arm 5. If the clamping force exceeds the set value, the PLC main control unit automatically stops the step pulse output, and the main control unit controls the brake 412 to start braking.

[0143] The above is only the preferred embodiment of the present invention, and it does not limit the patent scope of the present invention. Any equivalent structural transformation made by using the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, shall be included in the patent protection scope of the present invention by the same token.

Claims

1. A mechanical arm end fixture system, characterized in that, Comprising: A structural support frame; A combined connecting piece, located inside the structural support frame and linearly movable relative thereto; A transmission and control device, including a two-axis stepper motor and a linear guide rail located inside the structural support frame, two ball screws fixedly connected to the output shaft of the two-axis stepper motor, two moving nuts sleeved on the ball screws, and a linear motion slider mounted on the linear guide rail. The two moving nuts are respectively fixedly connected to the combined connecting pieces on both sides to drive the combined connecting pieces to move linearly, and the linear motion slider is fixedly connected to the combined connecting piece to guide the linear movement of the combined connecting piece and carry the load; A fixture arm, the end of which is hinged to the combined connecting piece, and drives the head of the fixture arm structure to move laterally through the linear movement of the combined connecting piece; A travel track frame, fixed below the structural support frame and provided with a sliding limit piece inside it for sliding connection with the fixture arm.

2. The robotic arm end fixture system according to claim 1, wherein linear guide rails are provided at both the top and bottom ends of the two-axis stepper motor, and linear motion sliders are fixed to both the top and bottom of the combined connecting piece; the transmission and control device further includes a housing for accommodating the two-axis stepper motor and the linear guide rail, and a brake mounted at the end of the ball screw. The moving nut is threadedly connected to the ball screw, and when the output shaft of the two-axis stepper motor rotates, it drives the ball screw to rotate and then drives the moving nut to move linearly.

3. The end-effector fixture system of the robotic arm according to claim 1, characterized in that, The housing includes a top plate and side plates on both sides of the top plate. The structural support frame includes a front plate, a rear plate, and a top support plate connecting the front plate and the rear plate. The top plate is fixed below the top support plate, and both ends of the two linear guide rails are respectively fixedly connected to the side plates on both sides. The two-axis stepper motor is located between the two linear guide rails.

4. The end-effector fixture system of the robotic arm according to claim 1, characterized in that, The combined connecting piece includes a moving block located in the middle and fixedly connected to the moving nut, two H-shaped connecting pieces fixed to the front and rear sides of the moving block, an I-shaped connecting flange fixed to the outside of the H-shaped connecting piece, a rotating shaft fixed to the end of the connecting flange, and a rotating shaft top cover mounted at the end of the rotating shaft and rotatably connected thereto. The end of the fixture arm is sleeved outside the rotating shaft and fixedly connected to the rotating shaft top cover. Linear motion sliders are fixed to both the upper and lower sides of the moving block.

5. The end effector system of the robotic arm according to any one of claims 1 to 4, characterized in that It further includes a top connecting flange fixed to the top of the structural support frame and an end clamping block fixed to the clamping end of the fixture arm; the sliding limit piece includes a motion bearing mounted on the fixture arm, and a chute for accommodating the motion bearing for sliding is provided on the travel track frame.

6. A control device for the end effector system of a robotic arm according to any one of claims 1 to 5, characterized in that, Comprising: A PLC main control unit, used to receive the control signal input by the user and generate a corresponding output signal according to the control logic; A motor driver, used to receive the stepping pulse signal controlled by the PLC main control unit and drive the motor to rotate precisely; An external control device, used to input motion commands and adjust the working characteristics of the fixture; A load detection system, used to detect the load of the two-axis stepper motor and the touch condition at the end of the fixture in real time; A feedback system, used to limit the number of rotation turns and the movement distance of the two-axis stepper motor; A power management system, used to supply power to the motor driver and the PLC main control unit to ensure the normal operation of each component; A protection module, used to prevent the two-axis stepper motor from having abnormal operation.

7. The control device of the robotic arm end fixture system according to claim 6, characterized in that, The PLC main control unit controls the motor driver by means of PTO control mode. The PTO control mode controls the movement speed, stroke and clamping size of the fixture arm by changing the pulse number and frequency of the input pulses of the two-axis stepping motor.

8. A control method for a control device of an end effector system of a robotic arm according to claim 6, characterized in that, It includes forward rotation control and reverse rotation control. The forward rotation control includes: after the PLC main control unit receives the forward rotation command information, it generates a forward or reverse pulse signal, the pulse frequency gradually decreases from the initial value, and the two-axis stepping motor gradually accelerates to the set speed and then gradually decelerates. The reverse rotation control includes: after the PLC main control unit receives the reverse rotation command signal, it generates a reverse pulse signal, the pulse frequency gradually increases from the initial value, and the motor gradually accelerates and stops after completing the specified number of turns.

9. The control method of the control device of the end effector system of the robotic arm according to claim 8, characterized in that, It includes a flexible clamping control method, and its steps include: The PLC main control unit controls the two-axis stepping motor to output a forward rotation pulse signal to drive the fixture to perform the clamping action. During the forward rotation of the output shaft of the two-axis stepping motor, the PLC main control unit real-time collects the sensor signals related to the load and the touch of the end. When it is detected that the load signal reaches the set threshold or the force of the end touch reaches a certain value, the PLC main control unit immediately stops outputting the pulse signal. The PLC main control unit records the pulse count value at the stop and calculates the actual number of turns of rotation as the determination basis for the fixture closing size. The PLC main control unit controls the brake at the end of the lead screw to ensure that the lead screw stops rotating after the fixture is clamped.

10. The control method of the control device of the end effector system of the robotic arm according to claim 8, characterized in that, It also includes the following steps: Use the load detection system to monitor the load condition of the two-axis stepping motor in real time. When the load exceeds the set threshold, the PLC automatically stops the pulse output of the two-axis stepping motor to stop the operation of the two-axis stepping motor. Transmit the magnitude of the clamping force of the fixture through the force sensor at the end of the fixture arm. If the clamping force exceeds the set value, the PLC main control unit automatically stops the stepping pulse output, and the main control unit controls the brake to start braking.

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