Electrically-driven intelligent constant force compensation system

Abstract

The invention is suitable for the technical field of robot automatic grinding, and provides an electric drive intelligent constant force compensation system which comprises an electric power control body which comprises a bottom plate and a shell. A linear motor stator, a linear motor rotor, a linear moving device, a force sensor, a displacement sensor, a gyroscope and a track clamping device are arranged on the top face of the bottom plate, reciprocating motion exists between the linear motor stator and the shell, labyrinth sealing is adopted, the linear motor stator and the linear motor rotor form a linear motor, and the linear motor stator and the linear motor rotor form a linear moving device. And the shell is controlled by a special driver and is used as a power source of electric power control, and the shell is provided with a heat dissipation device. According to the scheme, the stability of driving force is improved, the response speed of responding to external force changes is increased, sealing is achieved, meanwhile, the influence on output force is reduced to the minimum, the yield of high-precision polishing can be greatly increased, the polishing technological process is simplified, and the polishing efficiency is improved.

Description

Technical Field

[0001] This invention belongs to the field of robotic automated grinding technology, and particularly relates to an electrically driven intelligent constant force compensation system. Background Technology

[0002] Currently, the grinding industry is becoming increasingly automated, and the demand for high-precision grinding is also growing. Traditional manual grinding is not only inefficient but also prone to inconsistent quality, leading to high rework rates, and is gradually being replaced by automated grinding. Currently, there are two common methods for robotic automated grinding on the market: trajectory grinding and pneumatic constant-force tool flexible grinding. When robots grind along a trajectory, factors such as workpiece manufacturing, assembly, clamping, and the robot's precision can cause inconsistent material removal thickness, resulting in substandard grinding effects. Pneumatic constant-force tool flexible grinding offers significant improvement over trajectory grinding, but the inherent inaccuracy of compressed air as the driving force of pneumatic constant-force tools, with response times often exceeding 100ms, makes it difficult to maintain stable quality and meet high precision requirements in medium- to high-precision grinding scenarios.

[0003] Patent application CN202110971425.7 discloses a precision flexible grinding machine, comprising a grinding head, a cylinder, a hollow piston rod, a piston body, a front guide sleeve, a rear guide sleeve, a spring-loaded reset component, a universal bearing, a connecting seat, and a rotation-limiting component. This invention features a clever and rational structural design. The cylinder, consisting of the cylinder, hollow piston rod, and piston body, flexibly controls the grinding pressure and buffers the impact force on the grinding head through pneumatic pressure. Simultaneously, the connecting seat is movably connected to the hollow piston rod via a universal bearing, allowing the grinding head to swing freely and adapt to changes in the workpiece surface shape. With the elastic force of the spring-loaded reset component, it ensures consistent grinding force, avoiding uneven application or uneven application, thus improving grinding and polishing quality. Furthermore, the overall structure is compact, small in size, and lightweight, facilitating widespread application, especially suitable for use in robotic arms. The solution is a pneumatically driven force control, which is closest to electro-dynamic control.

[0004] Existing pneumatic constant force control systems use 0.5-6.0 bar compressed air to power cylinders, achieving relative constant force through valve regulation. Because pneumatic constant force control systems contain linear sliding mechanisms and electrical components, they typically require dust covers or dustproof cloths. Specific disadvantages and deficiencies are as follows:

[0005] 1. The thrust generated by the compressed air-driven cylinder is unstable, with dynamic accuracy typically fluctuating between 1-10N. Pneumatic control generally uses 0.5-6 bar compressed air as the driving force. The volume of this compressed air is prone to change and is also affected by temperature, humidity, and other components in the air, leading to inaccurate output force. Especially in scenarios where force control requires frequent adjustments, the deviation of the unsteady pneumatic cylinder is often even greater, typically reaching 1-10N. The magnitude of the force often directly affects the grinding effect, and fluctuations within this range often result in unsatisfactory grinding results.

[0006] 2. Compressed air has a slow dynamic response, typically within the range of 50-300ms. The speed of compressed air propagation in cylinders and valves generally does not exceed the speed of sound (340m / s). After the control system collects signals, calculates and issues valve control signals, the compressed gas driving the cylinder finally reaches the cylinder through valves, pipelines, and joints, generating force before stabilizing. During grinding, the changes in grinding force are often on the order of milliseconds, requiring the force control to adjust as quickly and timely as possible, ideally within 10ms. The 50-300ms response speed of pneumatic force control is insufficient for the precision requirements of medium-to-high precision grinding.

[0007] 3. Poor dustproof performance or resistance from the dustproof structure affects the accuracy of the grinding force. Since force controllers typically contain linear motion mechanisms, cylinders, and sensors, grinding often takes place in high-dust and high-humidity environments. Poor dustproof performance directly impacts the output accuracy of the force controller. Corrugated non-metallic materials are effective at preventing dust, working by using their own deformation to meet motion requirements while simultaneously providing a seal. The deformation direction of the corrugated non-metallic material is often opposite to the output force direction. The output force of the moving corrugated non-metallic material is non-linear; as speed increases, the force required for the same deformation increases accordingly, and it always acts in the opposite direction to the output force. Therefore, it affects the accuracy of the force controller, typically within the 0-1N range. Due to this non-linear resistance, it is difficult for the force controller to balance or compensate for this in the initial stage, affecting its dynamic accuracy and leading to poor grinding results.

[0008] Based on the above technical problems, this application proposes an electric drive intelligent constant force compensation system. Summary of the Invention

[0009] The purpose of this invention is to provide an electrically driven intelligent constant force compensation system to solve the problems mentioned in the background art.

[0010] To achieve the above objectives, the present invention provides the following technical solution: an electrically driven intelligent constant force compensation system, comprising an electric power control body, the electric power control body including a base plate and a shell, the top surface of the base plate being provided with a linear motor stator, a linear motor mover, a linear motion device, a force sensor, a displacement sensor, a gyroscope, and a track clamp. There is a reciprocating motion between the linear motor stator and the shell, and a labyrinth seal is used. The linear motor stator and the linear motor mover form a linear motor, controlled by a dedicated driver, serving as the power source for the electric power control. The shell is provided with a heat dissipation device. The force sensor is used to detect the output force of the linear motor and external forces in real time. The displacement sensor is used to detect the movement distance of the linear motor mover. The gyroscope is used to detect the angle between the electric power control device and gravity under different postures at the robot end effector. The heat dissipation device is used for heat dissipation of the linear motor and the entire force control shell. The shell is provided with a quick-connect cable connector.

[0011] Preferably, the linear motor mover is mounted on the linear motion device, and driven by the electromagnetic force inside the linear motor, the linear motor mover performs reciprocating linear motion along the linear motion device.

[0012] Preferably, a fixture for fixing the grinding tool is mounted on the linear motor mover, and the magnitude of the input current is controlled by the linear motor driver, thereby controlling the magnitude of the force applied by the grinding tool.

[0013] Preferably, the force sensor is installed between the linear motor actuator and the grinding tool to detect changes in force on the grinding tool in real time, thereby adjusting the output force of the linear motor to ensure a constant grinding force output.

[0014] Preferably, the displacement sensor is mounted on the linear motor mover, and the distance calibrator is fixed on the base. The displacement of the linear motor mover can be measured. Based on the data and frequency output by the displacement sensor, the average displacement data is calculated to obtain the average speed of the linear motor mover within milliseconds.

[0015] Preferably, the gyroscope is used to measure the angle of gravity along the direction of motion of the linear motor actuator when the electrodynamic control changes the posture of the robot end effector, and then the component force along the direction of motion is obtained by the cosine of the angle.

[0016] Preferably, the heat dissipation device typically consists of a fan and an air duct, and the system adjusts the airflow based on the temperature sensor inside the linear motor to dissipate heat.

[0017] Preferably, the linear motor includes, but is not limited to, a coreless linear motor or a linear motor with an iron core.

[0018] The present invention has at least the following beneficial effects:

[0019] The present invention provides an electric drive intelligent constant force compensation system, which improves the stability of the driving force, the response speed to changes in external force, and minimizes the impact on the output force while sealing, thereby significantly improving the yield of medium and high precision grinding, simplifying the grinding process, and improving grinding efficiency. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the internal structure of Embodiment 1 of the present invention;

[0021] Figure 2 This is a schematic diagram of the external structure of Embodiment 1 of the present invention;

[0022] Figure 3 This is a schematic diagram of the labyrinth seal in Embodiment 1 of the present invention;

[0023] Figure 4 This is a layout diagram of the surface structure of Embodiment 2 of the present invention;

[0024] Figure 5 This is a schematic diagram of the internal structure of Embodiment 2 of the present invention;

[0025] Figure 6 This is a schematic diagram of the external structure of Embodiment 2 of the present invention;

[0026] Figure 7 This is a schematic diagram of the labyrinth seal in Embodiment 2 of the present invention.

[0027] In the attached diagram, the following are the reference numerals: 1. Housing; 2. Base plate; 3. Quick-connect cable; 4. Tooling mounting plate; 5. Heat dissipation device; 6. Linear motor stator; 7. Linear motor mover; 8. Track clamp; 9. Linear movement device; 10. Force sensor; 11. Displacement sensor; 12. Gyroscope. Detailed Implementation

[0028] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] Please see Figure 1 , Figure 2 , Figure 3This embodiment provides a technical solution (coreless linear motor): an electrically driven intelligent constant force compensation system, including an electric power control body, which includes a base plate 2 and a shell 1. The top surface of the base plate 2 is provided with a linear motor stator 6, a linear motor mover 7, a linear movement device 9, a force sensor 10, a displacement sensor 11, a gyroscope 12, and a track clamp 8. There is a reciprocating motion between the linear motor stator 6 and the shell 1, and a labyrinth seal is used. The linear motor stator 6 and the linear motor mover 7 form a linear motor, which is controlled by a dedicated driver and serves as the power source for the electric power control. The shell 1 is provided with a heat dissipation device 5. The force sensor 10 is used to detect the output force of the linear motor and external forces in real time. The displacement sensor 11 is used to detect the moving distance of the linear motor mover 7. The gyroscope 12 is used to detect the angle between the electric power control device and gravity under different postures at the end of the robot. The heat dissipation device 5 is used for heat dissipation of the linear motor and the entire force control shell 1. The shell 1 is provided with a cable quick connector 3, and the tooling mounting plate 4 is rectangular.

[0031] The electrodynamic control system employs a linear motor with high dynamic response characteristics. Utilizing sensors such as force sensors, displacement sensors, and gyroscopes, and through dynamic modeling, it achieves precise closed-loop control via a microcomputer or PLC, realizing a grinding force output of 0-2000N with an accuracy of 0.03-0.5%FS. The gaps in the moving parts are sealed using a labyrinth seal.

[0032] The electrodynamic control system consists of a housing, base plate, linear motor mover and stator, linear motion device, force sensor, displacement sensor, gyroscope, heat dissipation device, and track clamp, such as... Figure 1 and Figure 2 As shown. The base plate is used to fix components such as the linear motor and linear motion device. The outer shell serves to prevent dust and protect internal components. A labyrinth seal is used between the motor stator and the outer shell for movement. The linear motor consists of a stator and a mover, controlled by a dedicated driver, serving as the power source for the electro-dynamic control system. Parameters output from force sensors, gyroscopes, and displacement sensors directly participate in the control of the linear motor's position, force, and speed. The force sensor is used to detect the motor's output force and external forces in real time. The displacement sensor is used to detect the movement distance of the linear motor's mover. The gyroscope is used to detect the angle between the electro-dynamic control device and gravity in different postures at the robot's end effector. The heat dissipation device is used for heat dissipation of the motor and the entire force control system's internal casing.

[0033] The mover of the linear motor is mounted on a linear motion device, while the stator is fixed. Driven by the electromagnetic force inside the linear motor, the mover reciprocates linearly along the linear motion device. Limit blocks, typically 15-50mm in diameter, are installed at both ends of the linear motor to limit the movement distance and protect the motor. A fixture for fixing a grinding tool is mounted on the mover. The input current is controlled by the linear motor driver, thereby controlling the force applied by the grinding tool. A force sensor is installed between the mover and the grinding tool to detect changes in force on the tool in real time, adjusting the motor's output force to ensure constant grinding force. A displacement sensor is mounted on the mover, and a calibrated distance measuring instrument is fixed to the base. This allows for the measurement of the mover's displacement. By averaging the displacement data based on the sensor's output data and frequency, the average velocity of the mover within milliseconds is obtained. Since the displacement sensor's output frequency is relatively high, generally greater than 1kHz, the average velocity over this time period can be approximated as the instantaneous velocity. The acceleration of the mover is then calculated by averaging the instantaneous velocity data. A gyroscope is used to measure the angle of gravity along the direction of motion of the linear motor's actuator as the robot's end effector changes posture. The component of the force along the direction of motion is then obtained using the cosine of the angle. The cooling system typically consists of a fan and air ducts. The system adjusts the airflow based on a temperature sensor inside the linear motor to dissipate heat and ensure continuous motor operation.

[0034] The linear motor experiences reciprocating motion between its mover and housing. To ensure smooth operation and minimize resistance from the seal, a labyrinth seal is employed. Figure 3 As shown, dust, polluted air, or humid gas need to pass through staggered channels to reach the interior. The staggered passage increases the resistance to dust or gas entry, and the positive pressure of the gas inside the electrodynamic control system further blocks it, thus effectively preventing dust.

[0035] Example 2

[0036] Please see Figure 4 , Figure 5 , Figure 6 , Figure 7 This embodiment provides a technical solution (with an iron core linear motor): an electric drive intelligent constant force compensation system, which differs from Embodiment 1 in that the tooling mounting plate 4 is arranged in a ring.

[0037] Example 3

[0038] Typically, there is a stable linear relationship between the output force and current of a linear motor. By controlling the current through the linear motor's driver, the magnitude of the motor's output force T can be precisely controlled. Its coefficient can be obtained by fitting the measured data of the motor current and output force. A force sensor can obtain the actual force F acting on the grinding tool, a displacement sensor can measure the linear motor's displacement x, velocity v, and acceleration a, and a gyroscope can measure the angle θ between the linear motor's direction of motion and gravity, thus allowing the calculation of the component force in the direction of motion. To obtain a constant output force for the electrodynamic control, it is necessary to balance the changing forces in the system by controlling the motor's output force. These changing forces mainly include the component of gravity along the direction of motion, the inertial force of the linear motor, and the resistance from the linear device. Based on the force components and the dynamic equilibrium equations, the dynamic model equations for the electrodynamic control are constructed as follows:

[0039] K·x+B·x'+M·x"=T-F0-M·g·cosθ;

[0040] Where: x is the displacement of the linear motor actuator, obtained through a displacement sensor;

[0041] x' is the first derivative of the displacement of the linear motor's mover, i.e., the velocity v, which is calculated from the displacement sensor data;

[0042] x" is the second derivative of the displacement of the linear motor mover, i.e., the acceleration a, which is calculated from the displacement sensor data;

[0043] K is the stiffness coefficient of the system, which is obtained by fitting test data;

[0044] B is the damping coefficient of the system, which is obtained by fitting test data.

[0045] M is the mass of the system, obtained through the output force of the force sensor and the linear motor;

[0046] T represents the output force of the motor, which is obtained by fitting the relationship between current and output force.

[0047] F0 is the set constant output force;

[0048] g is the acceleration due to gravity;

[0049] θ is the angle between the direction of linear motor motion and the direction of gravity, which is measured by a gyroscope.

[0050] Based on the above data and relationships, the current required by the linear motor is calculated in real time using a microcomputer and PLC computing unit, and the output force is kept constant by the linear motor driver. Since uncertain deviations may occur in the system, it is also necessary to compare the actual output force F (the force measured by the force sensor) with the actual set force F0, and perform negative feedback adjustment based on the deviation.

[0051] The response speed of linear motors is often in the microsecond range. Since electricity travels at the speed of light, the current loop of a linear motor can often complete the response in just 100-1000 ns. This response speed is more than a thousand times that of the pneumatic circuit. Therefore, electrodynamic control can complete the control in the millisecond range, which plays a decisive role in the dynamic accuracy of the output constant force.

[0052] Compared with common pneumatic control systems, the electrodynamic control system of this invention has the advantages of higher dynamic accuracy, faster response speed, and less impact of sealing on output force. Specifically:

[0053] 1. Replace one or more cylinder power systems with one or more linear motor power systems. Linear motors include, but are not limited to, coreless linear motors, iron-core linear motors, and magnetic shaft motors. The highly linear relationship between the current and output force of linear motors solves the problem of unstable linear relationship between cylinder output force and air pressure. Especially in dynamic adjustment processes, the advantages of electric force control are more obvious. Typically, the dynamic accuracy of pneumatic force control is affected by temperature, resistance, etc., and the output force fluctuates within a range of 1-20N (based on data evaluated from multiple brands and models on the market). Due to its stability and highly linear relationship, electric force control has an output force fluctuation range of 0-2N (theoretical calculations and prototype evaluation). In grinding applications, electric force control can output a more stable grinding force, resulting in better, more stable, and controllable surface quality after grinding. At the same time, for problems such as curved surface grinding, grinding tool wear, and workpiece deviation, stable output force can simplify the grinding process.

[0054] 2. Electrodynamic control can achieve millisecond-level response, which is thousands of times faster than pneumatic control. The speed of compressed air in cylinders and valves is no higher than the speed of sound (340 m / s), while electric current in a linear motor travels at the speed of light (3.0 x 10⁵ m / s). This high response speed not only improves dynamic accuracy but also shortens process time, increasing grinding efficiency by 1-10 times. Because electrodynamic control responds in milliseconds, compared to the tens or even hundreds of milliseconds of pneumatic control, the grinding process can achieve faster feed and faster robot posture switching, thus improving grinding efficiency.

[0055] 3. Labyrinth sealing method for moving parts. External gases or dust need to pass through a long, zigzag channel to enter the force controller, resulting in significant resistance and making entry difficult. Furthermore, the force controller has a positive gas discharge channel that flows outwards through the labyrinth, further increasing the resistance to dust or gas entry and ensuring a tight seal. Because there is no contact, the impact on the force controller's output force is minimized. Grinding environments are often characterized by high dust, high humidity, and high debris levels. Sealing components rely on the deformation of non-metallic materials, providing good sealing, but the friction between the seal and the sealing surface affects the constant force output. Dust covers rely on their own deformation for sealing, offering good sealing, but the resistance to deformation is often affected by various factors, directly impacting the constant force output. Simple shielding seals can minimize resistance, but the sealing effect is poor; dust, iron filings, or water entering can affect the lifespan of components and may also affect the linear motion device, thus impacting the output force.

[0056] The electro-dynamic control provided by this invention significantly improves the stability of the driving force, the response speed to changes in external force, and minimizes the impact on the output force while ensuring a sealed environment. This results in a substantial increase in the yield rate of medium-to-high precision grinding, simplifies the grinding process, and enhances grinding efficiency. Specific advantages are as follows:

[0057] ① Improved polishing yield: High-precision constant force output results in better surface consistency, more uniform and controllable removal of material, thus leading to a higher product yield.

[0058] ② Improve grinding efficiency: The force control can make more adjustments in the same amount of time to respond to changes in external force, allowing the process to grind with faster parameters, such as increasing the grinding feed speed and the robot posture change speed, which can effectively shorten the grinding time.

[0059] ③ Simplify the process flow: For complex curved surfaces, by selecting appropriate grinding tools and combining them with the high-speed and stable automatic compensation function of electric power control, the complex contouring trajectory can be simplified into simple straight lines, arcs, reciprocating oscillations, spirals, etc.

[0060] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. It will be apparent to those skilled in the art that the present invention is not limited to the details of the above exemplary embodiments, and that the present invention can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, the embodiments should be regarded as exemplary and non-limiting in all respects. The scope of the present invention is defined by the appended claims rather than the foregoing description. Therefore, it is intended that all changes falling within the meaning and scope of the equivalents of the claims be included within the present invention, and no reference numerals in the claims should be regarded as limiting the scope of the claims.

[0061] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An electrically driven intelligent constant force compensation system, characterized in that, The device includes an electric motor control body, which comprises a base plate (2) and a housing (1). The top surface of the base plate (2) is provided with a linear motor stator (6), a linear motor mover (7), a linear motion device (9), a force sensor (10), a displacement sensor (11), a gyroscope (12), and a track clamp (8). There is a reciprocating motion between the linear motor stator (6) and the housing (1), and a labyrinth seal is used. The linear motor stator (6) and the linear motor mover (7) form a linear motor, which is driven by a dedicated driver. Control, as the power source of the electric motor control, the outer shell (1) is provided with a heat dissipation device (5), the force sensor (10) is used to detect the output force of the linear motor and external action in real time, the displacement sensor (11) is used to detect the moving distance of the linear motor mover (7), the gyroscope (12) is used to detect the angle between the electric motor control device and gravity in different postures when the electric motor control is at the end of the robot, the heat dissipation device (5) is used for heat dissipation of the linear motor and the entire force control outer shell (1), and the outer shell (1) is provided with a cable quick plug (3).

2. The electrically driven intelligent constant force compensation system according to claim 1, characterized in that: The linear motor mover (7) is mounted on the linear moving device (9). Driven by the electromagnetic force inside the linear motor, the linear motor mover (7) moves back and forth in a straight line along the linear moving device (9).

3. The electrically driven intelligent constant force compensation system according to claim 1, characterized in that: The tooling for fixing the grinding tool is installed on the linear motor mover (7). The magnitude of the input current is controlled by the linear motor driver, thereby controlling the magnitude of the force applied by the grinding tool.

4. The electrically driven intelligent constant force compensation system according to claim 3, characterized in that: The force sensor (10) is installed between the linear motor mover (7) and the grinding tool to detect changes in force on the grinding tool in real time, thereby adjusting the output force of the linear motor to ensure constant grinding force output.

5. The electrically driven intelligent constant force compensation system according to claim 1, characterized in that: The displacement sensor (11) is installed on the linear motor mover (7) and the distance calibration gauge is fixed on the base. The displacement of the linear motor mover (7) can be measured. Based on the data and frequency output by the displacement sensor (11), the average displacement data is calculated to obtain the average speed of the linear motor mover (7) within milliseconds.

6. The electrically driven intelligent constant force compensation system according to claim 1, characterized in that: The gyroscope (12) is used to measure the angle of gravity along the direction of motion of the linear motor mover (7) when the electric motor controls the change of the robot's end posture, and then obtain the component force along the direction of motion through the cosine of the angle.

7. The electrically driven intelligent constant force compensation system according to claim 1, characterized in that: The heat dissipation device (5) is usually composed of a fan and an air duct. The system adjusts the air volume according to the temperature sensor inside the linear motor to dissipate heat.

8. The electrically driven intelligent constant force compensation system according to claim 1, characterized in that: The linear motors include, but are not limited to, coreless linear motors or linear motors with iron cores.

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