Electric gripper and operating method the same

Abstract

An electric gripper is used to grip an object, and the electric gripper includes a circuit board, a motor, a transmission mechanism, and a two-finger holder. The motor provides excess torque based on excess current supplied by the circuit board, thereby driving the transmission mechanism. The transmission mechanism drives the two-finger holder to move in a closing direction based on the excess torque, thereby providing excess gripping force to grip the object. After gripping the object, the electric gripper maintains the gripping force of the two-finger holder within a specific range, with the upper limit being the excess gripping force, through the transmission mechanism.

Description

[Technical Field]

[0001] This invention relates to an electric gripper and its operating method, and more particularly to an electric gripper and its operating method that can significantly improve the gripping force. [Previous Technology]

[0002] In the prior art, increasing the clamping force of electric grippers generally involves maximizing the torque of the motor rotor itself. Generally, increasing the torque of electric grippers is achieved by either increasing the gear ratio or increasing the number of windings in the windings. However, using gear ratio amplification inevitably sacrifices the closing speed of the electric grippers, resulting in no reduction in operating time. Therefore, this technology is not the optimal way to increase clamping force.

[0003] On the other hand, with the technology using a higher number of coils, a higher number of coils is required to achieve greater torque output, resulting in a larger motor size requirement. Therefore, this technology cannot significantly increase the motor torque within the limited gripper space. Furthermore, to ensure the motor does not overheat during operation, thus preventing damage to the motor coils and drive control board, the motor's current limit is generally restricted to not exceeding the rated current. Due to these limitations, electric grippers with the same clamping force are inevitably larger and heavier than pneumatic grippers, making this a bottleneck in the development of high-clamping-force electric grippers and hindering their market adoption.

[0004] Therefore, how to design an electric gripper and its operation method so that the gripping force of the electric gripper can be multiplied and the output burden of the motor can be greatly reduced is a major research topic that the creator of this case intends to conduct. [Summary of the Invention]

[0005] To solve the above problems, this disclosure provides an electric gripper to overcome the problems of the prior art. Therefore, the electric gripper disclosed herein is used to grip objects, and the electric gripper includes a circuit board, a motor, a transmission mechanism, and two-finger holders. The circuit board provides an excess current exceeding the rated current at a first moment, and the motor is coupled to the circuit board to provide excess torque according to the excess current. The transmission mechanism includes a gear set, a screw set, and a linear guide rail, and the gear set is connected to the motor. The screw set includes a rod body, with left-hand and right-hand threads respectively formed at both ends of the rod body, and the motor drives the gear set through the excess torque to control the rotation of the rod body. The linear guide rail is disposed on one side of the screw set, and the two-finger holders are respectively screwed onto the left-hand and right-hand threads. The two-finger holders are engaged with the linear guide rail to reciprocate along the linear guide rail according to the rotation of the rod body. The motor drives the two-finger holder to move in the closing direction through excess torque, so as to provide excess clamping force to clamp the object through the closing of the two-finger holder. In the second time after clamping the object, the transmission mechanism maintains the clamping force of the two-finger holder within a specific range with an upper limit value of the excess clamping force.

[0006] To solve the above problems, this disclosure provides an electric gripper to overcome the problems of the prior art. Therefore, the electric gripper disclosed herein is used to grip an object, and the electric gripper includes a circuit board, a motor, a transmission mechanism, and two-finger holders. The circuit board provides an excess current exceeding the rated current at a first moment, and the motor is coupled to the circuit board to provide excess torque according to the excess current. The transmission mechanism includes a gear set and a meshing transmission mechanism, and the gear set is connected to the motor. The meshing transmission mechanism is connected to the gear set, and the motor drives the gear set through the excess torque to control the rotation of the meshing transmission mechanism in the vertical direction of the output shaft of the gear set. The two-finger holders each include a set of teeth, and the sets of teeth of the two-finger holders reciprocate accordingly according to the rotation of the meshing transmission mechanism. The motor drives the two-finger holders to move in the closing direction through the excess torque to provide excess clamping force to grip the object through the closing of the two-finger holders, and at a second moment after gripping the object, the meshing transmission mechanism maintains the clamping force of the two-finger holders within a specific range where the upper limit is the excess clamping force.

[0007] To solve the above problems, this disclosure provides an operating method for an electric gripper to overcome the problems of the prior art. Therefore, the operating method of the electric gripper disclosed herein is used to control the electric gripper to hold an object, and the operating method includes the following steps: (a) providing current to the motor of the electric gripper, and the motor providing torque according to the current to drive a transmission mechanism. (b) the transmission mechanism drives the two-finger holder to move in a closing direction or away from the closing direction. (c) when the two-finger holder is moving, providing an excess current exceeding the rated current to the motor at a first moment. (d) the motor providing excess torque according to the excess current to drive the transmission mechanism, so as to provide an excess clamping force to hold the object by controlling the closing of the two-finger holder through the transmission mechanism. (e) maintaining the clamping force of the two-finger holder within a specific range where the upper limit is the excess clamping force through the transmission mechanism.

[0008] The main objective and effect of this invention is that the electric gripper disclosed herein uses an operation method of instantaneous over-rated current combined with a self-locking function to double the clamping force of the electric gripper and greatly reduce the output burden of the motor, thereby achieving the effect of significantly improving the clamping force of the electric gripper.

[0009] In order to further understand the technology, means and effects adopted by the present invention to achieve the intended purpose, please refer to the following detailed description and drawings of the present invention. It is believed that the purpose, features and characteristics of the present invention can be understood in depth and in detail from them. However, the accompanying drawings are provided for reference and illustration only and are not intended to limit the present invention.

Implementation Method

[0024] The technical content and detailed description of the present invention are explained below with reference to the accompanying drawings:

[0025] Please refer to Figure 1, which is a structural schematic diagram of the first embodiment of the electric gripper disclosed herein. The electric gripper 100 is mainly used to grip the object 200 (hereinafter referred to as object 200), and the electric gripper 100 includes a circuit board 1, a motor 2, a transmission mechanism 3, and a two-finger holder 4. The circuit board 1 is electrically connected to the motor 2, and the circuit board 1 may include a drive circuit (not shown) and a controller (not shown) for controlling the motor 2 by controlling the drive circuit. The controller (not shown) can control the drive circuit by receiving external control signals, so as to adjust the speed and torque of the motor 2 by adjusting parameters such as voltage V, current I, and frequency f supplied to the motor 2 through the control drive circuit (not shown). Preferably, the motor 2 can be a brushless DC motor (BLDC) or a permanent magnet synchronous motor (PMSM), and its speed and torque can be determined by the magnitude of the control current, but it is not limited thereto. All types of motors 2 that are applicable to the electric gripper 100 should be included in the scope of this embodiment.

[0026] In one embodiment, the circuit board 1 of FIG1 can be placed at a remote end, but is not limited to the position shown in FIG1. ​​It can be placed at the near end of the electric gripper 100 and control the motor 2 by transmitting parameters such as voltage V, current I, and frequency f via wired or wireless means. Alternatively, the circuit board 1 can be composed of multiple small circuit boards, and the external control signal is transmitted from the small circuit board at the remote end to the small circuit board at the near end equipped with a drive circuit (not shown), so that the drive circuit (not shown) of the small circuit board at the near end provides parameters such as voltage V, current I, and frequency f to control the motor 2. Therefore, this disclosure does not limit the composition, placement, and configuration of the circuit board 1.

[0027] The transmission mechanism 3 connects to the rotor of the motor 2, and includes a gear set 32, a screw set 34, and a linear guide rail 36. The gear set 32 ​​may include a plurality of meshing gears, and the input gear of the gear set 32 ​​is sleeved on the rotating shaft of the motor 2, and the torque of the motor 2 can be increased by the linkage of the plurality of gears. The screw set 34 includes a rod body 340, and the two ends of the rod body 340 respectively form a left-hand thread 342 and a right-hand thread 344 spiraling towards the center of the rod body 340. The output gear of the gear set 32 ​​is sleeved on the rod body 340, so that the rotation of the motor 2 can drive the gear set 32 ​​to control the rotation of the rod body 340. The linear guide rail 36 may be arranged on one side of the screw set 34 and parallel to the rod body 340.

[0028] The two-finger plate holder 4 may include a claw 40, a nut 42, and a moving part 44, and the nut 42 of the two-finger plate holder 4 may be screwed into the left thread 342 and the right thread 344 of the rod body 340 respectively. The moving part 44 of the two-finger plate holder 4 is respectively engaged with the slide groove 360 ​​of the linear slide rail 36, so that the moving part 44 can reciprocate linearly in the direction given by the linear slide rail 36, thus allowing the two-finger plate holder 4 to reciprocate in the linear slide rail 36 according to the rotation of the rod body 340. Therefore, the circuit board 1 can provide parameters such as voltage V, current I, and frequency f to control the rotation of the motor 2, so that the motor 2 can drive the gear set 32 ​​to control the rotation of the rod body 340, thereby driving the two-finger plate holder 4 to move in the forward direction (i.e., the two-finger plate holder 4 towards the closing direction) or the reverse direction (i.e., the two-finger plate holder 4 towards the away direction) in the given direction. When the two-finger holder 4 moves in the closing direction, the electric gripper 100 can grip the object 200 by closing the two-finger holder 4. Conversely, when the two-finger holder 4 moves in the moving away direction, the electric gripper 100 can release the object 200 by moving the two-finger holder 4 away.

[0029] Furthermore, one of the features of the electric gripper 100 disclosed herein is that it uses an instantaneous overcurrent operation method combined with a self-locking function to double the clamping force of the electric gripper 100. Moreover, because the electric gripper 100 disclosed herein has a self-locking function, the output load on the motor 2 can be greatly reduced. Therefore, the motor 2 only needs to adjust the instantaneous current to maintain the clamping force of the electric gripper 100. In this way, the motor 2 can significantly increase the clamping force of the electric gripper 100 even under instantaneous overcurrent operation.

[0030] Specifically, when the electric gripper 100 of this disclosure begins to move in the closing direction until the two-finger holder 4 grips the object 200 (hereinafter referred to as the first moment), the circuit board 1 controls the drive circuit to provide excess current Ier to the motor 2 according to the external control signal. Generally, the rated current, rated power, rated torque, and other values ​​are clearly marked on the nameplate of the motor 2. The rated current refers to the current allowed by the motor 2 under rated environmental conditions (ambient temperature, sunlight, altitude, installation conditions, etc.) when the motor 2 operates continuously for a long time (e.g., but not limited to more than 5 minutes) without triggering overcurrent or overtemperature protection. Furthermore, when the rated current is exceeded, the motor 2 will inevitably trigger overcurrent or overtemperature protection within a short time (e.g., but not limited to less than 5 minutes).

[0031] Then, the motor 2 provides excess torque Ter according to the excess current Ier, driving the gear set 32 ​​and the screw set 34, causing the two-finger holder 4 to move in the closing direction according to the excess torque Ter, so as to provide excess clamping force Fer to clamp the object 200. Furthermore, when the two-finger holder 4 clamps the object 200 and the electric gripper 100 moves to the appropriate position to release the two-finger holder 4 (hereinafter referred to as the second time), the transmission mechanism 3 can maintain the clamping force of the two-finger holder 4 within a specific range with an upper limit value of the excess clamping force Fer (for example, but not limited to 30% below the excess clamping force Fer) through mechanical actuation. In this way, the electric gripper 100 disclosed herein can achieve a significant increase in clamping force compared to conventional electric grippers.

[0032] The transmission mechanism 3 can maintain the clamping force of the two-finger holder 4 within a specific range through a locking device (not shown). When the two-finger holder 4 clamps the object 200, the transmission mechanism 3 can actively lock the two-finger holder 4 using the locking device (not shown), ensuring the clamping force of the two-finger holder 4 remains within a specific range. Alternatively, the transmission mechanism 3 can be designed to have a self-locking function. Specifically, the left thread 342 and right thread 344 of the rod 340 disclosed herein have a lead angle α, and the nut 42 of the two-finger holder 4 has frictional resistance with respect to the left thread 342 and the right thread 344, respectively. When the lead angle α is below a certain angle (i.e., low lead angle) and the frictional resistance is above a certain resistance (i.e., high frictional resistance), the finger holder 4 of the electric gripper 100 has a self-locking irreversible characteristic after displacement (i.e., the rod 340 cannot be driven by the finger holder 4), so that in the second time after the two-finger holder 4 clamps the object 200, the transmission mechanism 3 can maintain the clamping force of the two-finger holder 4 within a certain range through the self-locking function.

[0033] Please refer to Figures 2A-2C for further information on why the left thread 342 and right thread 344 of the rod 340 use a low lead angle and a high frictional resistance design to achieve the self-locking irreversible characteristic. In Figure 2A, the lead angle α of the left thread 342 and right thread 344 is: tan α = P / πd2. Furthermore, in Figure 2B, the condition for the internal thread of the nut 42 of the finger seat 4 to be self-locking is related to the direction of the force applied by the object. That is, to achieve the self-locking condition, the vector f must be greater than the vector F, so that the object m will not continuously displace in the direction of the vector F (i.e., frictional resistance). Therefore, the curve in Figure 2C can be deduced from Figures 2A-2B that the transmission efficiency η = (1-μ*tan*α) / (1+μ*tan*α), and it can have a certain self-locking capability below 50% (where α is the lead angle and μ is the frictional resistance). Therefore, when the lead angle α is below a certain angle (e.g., but not limited to, below 5°) and the frictional resistance is above a certain resistance (e.g., but not limited to, above 0.1), the transmission mechanism 3 can have a self-locking function.

[0034] Referring to Figure 1, the transmission mechanism 3 may optionally include an unlocking knob 38. The unlocking knob 38 may be disposed at one end of the rod 340 and is axially connected to the rod 340. The unlocking knob 38 is used to rotate the rod 340 to apply sufficient rotational force, so that the nut 42 can overcome friction and rotate, thereby releasing the self-locking function and releasing the clamping force of the two-finger holder 4. In this way, the finger holder 4 can be unlocked by using the unlocking knob 38 when needed (e.g., but not limited to maintenance, foreign object removal, etc.). In addition, the transmission mechanism 3 has a variety of other ways to release the self-locking function (e.g., but not limited to, vibration, impact, or reverse friction unlocking), which will not be described in detail here.

[0035] Because the electric gripper 100 disclosed herein possesses a self-locking and irreversible characteristic, when the motor 2 drives the screw assembly 34 to perform the closing action of the finger holder 4 to clamp the object 200 via the gear set 32, and the torque of the motor 2 rises to a set value (i.e., at the second moment, the clamping force is within a specific range), the circuit board 1 can stop controlling the motor 2. For example, but not limited to, the circuit board 1 can stop outputting parameters such as voltage V, current I, and frequency f to prevent the motor 2 from operating, or the circuit board 1 can de-energize the motor 2 to shut off its output. Furthermore, because the screw assembly 34 uses a low lead angle and a high frictional resistance design, it inherently possesses a self-locking and irreversible characteristic, thus allowing the two-finger holder 4 to maintain a clamping force slightly lower than the clamping force when closed (i.e., within a specific range), preventing the two-finger holder 4 from easily loosening and causing the object 200 to fall.

[0036] In addition to the aforementioned safety design that ensures the object 200 will not fall when the motor 2 is powered off, this disclosure further utilizes the method of the motor 2 exceeding its rated load by several times for a short period of time (i.e., providing excess current Ier) to increase the maximum clamping force of the electric gripper 100. Therefore, compared to the electric grippers of the prior art, the electric gripper 100 of this disclosure can achieve the same clamping force while reducing the size of the motor 2, thereby achieving the advantages of miniaturization and weight reduction of the electric gripper 100.

[0037] On the other hand, referring to FIG1, the electric gripper 100 may optionally include a position sensing circuit 5. The position sensing circuit 5 is disposed on the circuit board 1 and is used to sense the position of the rotor of the motor 2 and provide a position signal (not shown). The position sensing circuit 5 is, for example, but not limited to, a circuit composed of an encoder or a Hall element. In addition to providing a position signal (not shown) for the circuit board 1 to determine whether the motor 2 has malfunctioned or is abnormal, the position sensing circuit 5 can also be used to detect the release of the motor 2. Specifically, after the two-finger gripper 4 clamps the object 200 (i.e., at the second time), the circuit board 1 can provide a current lower than the rated current (for example, but not limited to, 30% of the rated current) to the motor 2, so that the motor 2 provides a torque lower than the rated torque, so that the circuit board 1 can determine whether the rotor has shifted based on the position signal (not shown), and thus detect whether the object 200 has accidentally fallen during the clamping operation. Furthermore, since the motor 2 is not turned off during the operation of the electric gripper 100, but operates with reduced torque, if the object 200 accidentally falls during the gripping process, the rotor of the motor 2 will shift due to the two-finger holder 4 not being tightly closed. This causes the position sensing circuit 5 to detect the situation and provide a corresponding position signal (not shown). In this way, the position signal (not shown) indicates that the object 200 has accidentally fallen, thereby improving the safety of the electric gripper 100 and increasing its overall operational efficiency.

[0038] Please refer to Figure 3, which is a structural schematic diagram of the second embodiment of the electric gripper disclosed herein, and refer to Figures 1-2C in conjunction. The operation of Figure 3 is largely similar to that of Figure 1, in that the motor 2 drives the gear set 32 ​​to control the closing action of the finger holder 4 to grip the object 200. The difference lies in the slight changes in the transmission mechanism 3 and the finger holder 4. Specifically, the transmission mechanism 3 in Figure 3 includes a gear set 32 ​​and a meshing transmission mechanism 35. The gear set 32 ​​may include a plurality of meshing gears, and the input gear of the gear set 32 ​​is sleeved on the rotating shaft of the motor 2, and the torque of the motor 2 can be increased by the linkage of the plurality of gears. The meshing transmission mechanism 35 is sleeved on the output gear of the gear set 32, so that the rotation of the motor 2 can drive the gear set 32 ​​to control the rotation of the meshing transmission mechanism 35 in the vertical direction of the output shaft of the gear set 32, and the output shaft of the meshing transmission mechanism 35 is connected to the two finger holders 4.

[0039] The two-finger gripper 4 includes a gear set 46, and the gear set 46 of the two-finger gripper 4 meshes with the moving component 44. The moving component 44 is shaft-connected to the meshing transmission mechanism 35, so as to perform reciprocating motion according to the rotation of the meshing transmission mechanism 35. Therefore, the circuit board 1 (not shown in FIG3, which is disposed near the electric gripper 100) can provide parameters such as voltage V, current I, and frequency f to control the rotation of the motor 2, so that the motor 2 can drive the gear set 32 ​​to control the rotation of the output gear of the meshing transmission mechanism 35, thereby driving the gear set 46 of the two-finger gripper 4 to move in a given direction in the forward direction (i.e., the gear set 46 of the two-finger gripper 4 moves towards the closing direction) or in the reverse direction (i.e., the gear set 46 of the two-finger gripper 4 moves away from the direction). When the two gear set 46 moves towards the closing direction, the electric gripper 100 can clamp the object 200 through the closing of the two gear set 46. Conversely, when the two-tooth row group 46 moves away, the electric gripper 100 can release the object 200 by moving away from the two-tooth row group 46.

[0040] The meshing transmission mechanism 35 can have various orthogonal output structures. Taking Figure 3 as an example, the meshing transmission mechanism 35 may include a worm 352 and a worm wheel 354. The worm 352 includes a rod body 352A, and a first thread 352B is formed on the rod body 352A in a specific direction, and the worm wheel 354 includes a second thread 354A. The axis of the worm wheel 354 is perpendicular to that of the rod body 352A, and it rotates along the vertical direction of the output shaft of the gear set 32 ​​by screwing the second thread 354A onto the first thread 352B. The moving part 44 of the two-finger plate holder 4 is shaft-connected to the worm wheel 354, so that the moving part 44 rotates with the rotation of the worm wheel 354. In one embodiment, the difference between Figure 1 and Figure 3 is that the design of the worm 352 and worm wheel 354 in Figure 3 can provide a larger reduction ratio and generate a larger torque, but requires a larger space. Therefore, the electric gripper 100 in Figure 1 is suitable for environments where the object 200 is small and the space for configuring the electric gripper 100 is relatively limited. Conversely, the electric gripper 100 in Figure 3 is suitable for environments where the object 200 is large and the space for configuring the electric gripper 100 is large.

[0041] Similarly, the electric gripper 100 in Figure 3 can also drive the gear set 32 ​​and the meshing transmission mechanism 35 through the excess torque Ter, so that the two-finger holder 4 moves in the closing direction according to the excess torque Ter, so as to provide excess clamping force Fer to clamp the object 200. Furthermore, when the two-finger holder 4 clamps the object 200 and the electric gripper 100 moves to the appropriate position to release the two-finger holder 4 (hereinafter referred to as the second time), the transmission mechanism 3 can maintain the clamping force of the two-finger holder 4 within a specific range with an upper limit value of the excess clamping force Fer (for example, but not limited to 30% below the excess clamping force Fer) through mechanical actuation.

[0042] In addition, the worm 352 and worm wheel 354 can also use a design with a large reduction ratio and a large frictional resistance, so that the finger holder 4 of the electric gripper 100 has a self-locking irreversible characteristic after displacement. Specifically, the first thread 352B of the worm 352 has a lead angle α, and there is frictional resistance between the first thread 352B and the second thread 354A. When the lead angle α is below a certain angle (i.e., low lead angle) and the frictional resistance is above a certain resistance (i.e., large frictional resistance), the finger holder 4 of the electric gripper 100 has a self-locking irreversible characteristic after displacement (i.e., the worm 352 cannot be driven by the finger holder 4), so that in the second moment after the two finger holders 4 clamp the object 200, the transmission mechanism 3 can maintain the clamping force of the two finger holders 4 within a certain range through the self-locking function (for specific principles, please refer to Figures 2A~2C).

[0043] Furthermore, the electric gripper 100 of FIG3 may also include an unlocking knob 38. The unlocking knob 38 is disposed on the gear set 32 ​​and is also used to rotate the rod 352A to apply sufficient rotational force, so that the two-tooth set 46 can overcome the friction and rotate the rod 352A, thereby releasing the self-locking function and releasing the clamping force of the two-finger holder 4. Similarly, the electric gripper 100 of FIG3 may also stop controlling the motor 2 when the torque of the motor 2 rises to a set value (i.e., at the second time, when the clamping force is within a specific range). Alternatively, the electric gripper 100 may also selectively include a position sensing circuit 5 to provide a position signal (not shown) for release detection. In one embodiment, the circuit structure, connection relationship and operation method not specifically described in FIG3 are similar to those in FIG1, so they can be referred to in conjunction with the description in FIG1, and will not be repeated here.

[0044] Please refer to Figure 4A, which is a waveform diagram of the motor current in the first embodiment of the present disclosure, and Figure 4B, which is a clamping force curve diagram of the motor current in Figure 4A applied to the present disclosure. Also refer to Figures 1-3. Since the electric gripper 100 uses a permanent magnet synchronous motor (or a brushless DC motor), the motor 2 employs field-guided control, controlling the motor torque through current commands. Therefore, based on the maximum current of the motor 2, it can instantaneously output N times the rated torque (i.e., excess torque Ter). Furthermore, since the electric gripper 100 has a self-locking function, only an instantaneous input of excess torque Ter is needed to maintain the clamping force of the two-finger holder 4. Therefore, by providing an input of N times the rated torque by the motor 2, the clamping force of the two-finger holder 4 is also increased by N times.

[0045] Furthermore, in Figure 4A, the electric gripper 100 disclosed herein mainly utilizes the circuit board 1 to provide an instantaneous excess current Ier to the motor 2. Figure 4B shows that the electric gripper 100 instantaneously increases the current I of the motor 2 to 120%, 160%, and 200% of the rated current Ir (i.e., excess current Ier) at the same closing speed (8 mm / s) (i.e., under the same rotational speed). After the operation of the excess current Ier is maintained for a short period of time (i.e., the first time T1, for example, but not limited to 50 ms), the current I of the motor 2 is continuously operated below the rated current Ir (i.e., within the second time T2, for example, but not limited to 30% of the rated current Ir) to provide a release detection function.

[0046] Referring to Figure 4B, when the current I of motor 2 instantaneously rises to 120%, 160%, and 200% of the rated current Ir, the clamping force of the electric gripper 100 also increases with the excess current Ier. Furthermore, since the electric gripper has a self-locking function, even if the current I of motor 2 drops below 30% of the rated current Ir after the running time (i.e., within the second time T2), the clamping force of the electric gripper 100 can still be maintained within a specific range Ra whose upper limit is the excess clamping force Fer (for example, but not limited to 30% below the excess clamping force Fer), and the phenomenon of a significant decrease in clamping force due to a significant drop in current I will not occur. Therefore, if the clamping force of the electric gripper 100 is to be increased, the excess current Ier can be increased by the circuit board 1 at the first time T1 (for example, from the original 120% of the normal operation to 200%), so that the motor 2 can increase the excess torque Ter, thereby increasing the excess clamping force Fer by increasing the excess torque Ter.

[0047] Please refer to Figure 5A, which is a waveform diagram of the second embodiment of the motor current disclosed herein, and Figure 5B, which is a clamping force curve diagram of the motor current of Figure 5A applied in this disclosure. Also refer to Figures 1-4B. The difference between Figure 5A and Figure 4A is that Figure 5A shows the electric gripper 100 increasing the same excess current Ier (for example, but not limited to, the current I is increased to 140% of the rated current Ir) at different closing speeds (5mm / s, 10mm / s, 20mm / s) (i.e., under different rotational speeds). Furthermore, as can be seen from Figure 5B, the faster the closing speed of the electric gripper 100, the greater the clamping force of the electric gripper 100. Therefore, to increase the clamping force of the electric gripper 100, the voltage V, current I, frequency f, and other parameters of the motor 2 can be adjusted via the circuit board 1 at the first moment T1 (depending on the type of motor 2) to increase the speed of the motor 2 (for example, from the original 5 mm / s conventional operation to 20 mm / s). This allows the motor 2 to increase the excess clamping force Fer by increasing its speed. It is worth mentioning that, in one embodiment, this disclosure can also combine the adjustment of the excess current Ier in Figure 4A and the adjustment of the motor 2 speed in Figure 5A to significantly increase the clamping force of the electric gripper 100.

[0048] On the other hand, the electric gripper 100 disclosed herein provides a better overcurrent and overtemperature protection mechanism, thereby improving operational stability and safety. Specifically, since this disclosure uses an overcurrent Ier operating method combined with a self-locking function, the clamping force of the electric gripper 100 can be doubled. However, a better protection mechanism is needed for the overcurrent Ier operating method to avoid the electric gripper 100 easily failing unexpectedly during operation and causing safety concerns. Therefore, this disclosure specifically establishes an overcurrent and overtemperature protection mechanism for the overcurrent Ier operating method to ensure the safety of the electric gripper.

[0049] Please refer to Figure 6A, which is a graph of instantaneous current versus operating time disclosed herein, and also refer to Figures 1-5B. Overcurrent protection is a protection function to prevent the motor 2 from overheating. By comparing the ratio of the excess current Ier to the rated current with the first time (upper limit), it can be determined at what excess current Ier (ratio) the duration of the first time is permissible. Furthermore, once the permissible duration is exceeded, the electric gripper 100 will activate the overcurrent protection mechanism to avoid damage to the electric gripper 100 due to overcurrent. Specifically, the electric gripper 100 disclosed herein (refer to Figures 1 and 3) may include a current detection circuit (not shown). The current detection circuit (not shown) is disposed on the circuit board 1 and is used to sense the current I supplied by the circuit board 1 to the motor 2 and provide a current signal to determine whether the operation of the circuit board 1 and the motor is normal.

[0050] Furthermore, the current detection circuit (not shown) can also be applied to the overcurrent protection mechanism during the operation of the electric gripper 100. Specifically, the current detection circuit (not shown) can sense the magnitude of the excess current Ier provided by the circuit board 1 to the motor 2 at the first moment, and the circuit board 1 calculates the allowable duration of the first moment based on the excess current Ier. When the duration of the first moment exceeds the preset time threshold of the circuit board 1, the electric gripper 100 enters the overcurrent protection mechanism to prevent the motor 2 from overheating. Under the overcurrent protection mechanism, the electric gripper 100 can enter a standby state until the temperature of the motor 2 drops below a predetermined temperature before it can continue to operate. Finally, as can be seen from Table 1 below, when the excess current Ier (proportion) is larger, the allowable duration is shorter, but the clamping force will be larger. Therefore, the higher the excess current Ier is within the allowable conditions of the electric gripper 100 (e.g., but not limited to 280%, 300%, etc.), the better, as it can provide a larger clamping force. Instantaneous current (proportional) runtime 120% 263.8s 140% 35.2s 160% 17.6s 180% 11.2s 200% 8s 220% 6.1s 240% 4.8s 260% 3.9s 280% 3.3s 300% 2.8s Table 1: Schematic diagram of the relationship between instantaneous current and running time.

[0051] Please refer to Figure 6B for a schematic diagram of the configuration of the heat-generating elements disclosed herein, and also refer to Figures 1-6A. In addition to the overcurrent protection mechanism shown in Figure 6A, this disclosure also includes an overtemperature protection mechanism. Specifically, Figure 6B shows the power components of the electric gripper 100 that accumulate significant heat during operation. In the entire electric gripper 100, the power components prone to heat generation are generally the position sensing circuit 5 (as shown in small figure (a)) and the power switch Q in the drive circuit (as shown in small figure (b), for example, but not limited to, a MOSFET). Therefore, the overtemperature protection mechanism primarily targets these two types of power components. When the temperature of one of them exceeds a temperature threshold, the electric gripper 100 will activate the overtemperature protection mechanism.

[0052] Furthermore, since the electric gripper 100 disclosed herein operates at an overcurrent Ier for a short period of time, these heat-generating components will also rapidly accumulate a large amount of heat due to the operating conditions of the overcurrent Ier. Therefore, to prevent these heat-generating components from burning out due to overheating, the electric gripper 100 disclosed herein (refer to Figures 1 and 3) may include a temperature sensing circuit (not shown). The temperature sensing circuit (not shown) is disposed around the heat-generating power components in the circuit board 1 and is used to sense the ambient temperature around these heat-generating components in the circuit board 1 and provide a temperature signal. When the circuit board 1 determines that the ambient temperature has exceeded the preset temperature threshold of the circuit board 1, the electric gripper 100 enters over-temperature protection to prevent the heat-generating components from burning out due to overheating.

[0053] Please refer to Figure 7A, which is a waveform diagram of the first operation mode of the overcurrent protection mechanism disclosed herein, and Figure 7B, which is a waveform diagram of the second operation mode of the overcurrent protection mechanism disclosed herein. Also refer to Figures 1-6B. Figures 6A-6B mainly illustrate the overcurrent and overtemperature protection mechanisms of the electric gripper 100 under a single clamping operation. Although the duration limitation of the overcurrent and temperature detection can protect against single clamping, under continuous and rapid high-current clamping, the heat generated by these heat-generating components may not be completely dissipated and may gradually accumulate, thus easily damaging the motor 2. Therefore, this disclosure incorporates an I 2T current limiting algorithm to provide a more comprehensive protection mechanism.

[0054] Specifically, the electric gripper 100 disclosed herein (refer to Figures 1 and 3) may include a current accumulation circuit (not shown). The current accumulation circuit (not shown) is configured on the circuit board 1 and calculates the accumulated variable based on the excess current Ier and the first time. When the circuit board 1 determines that the accumulated variable has exceeded the preset accumulation threshold of the circuit board 1, the electric gripper 100 enters over-cycle protection. In this way, the clamping speed can be limited in a short period of time by means of the current accumulation circuit (not shown). When the excess current Ier is larger, the next clamping time can be extended by the calculation of the I 2T current limiting algorithm, allowing the current accumulation circuit (not shown) sufficient time to release (that is, to correspond to the heat dissipation time of some easily heated components), thus achieving the speed limiting mechanism. In this way, the situation of damage to the motor under continuous and rapid high current clamping can be avoided. The I 2T formula is as follows:

[0055] I 2T setting value = (peak current limit 2 - continuous current limit 2) * I 2T time limit…(Equation 1)

[0056] I 2T accumulated variable 𝑛 +1=I 2T accumulated variable 𝑛+(actual current output 𝑛 +1 2-continuous current limit 2)*update cycle…(Equation 2)

[0057] Therefore, from Equations 1 and 2 above, it can be seen that when the current I is smaller, the time for the accumulated variable to dissipate will be shorter, allowing the current accumulation circuit (not shown) to release more quickly. Conversely, when the current I is larger, the time for the accumulated variable to dissipate will be longer, and if there is not enough time for release, the accumulated variable will also accumulate, requiring even longer to release completely.

[0058] Referring to Figure 7A, when the excess current Ier is 5A, the accumulated variable Va, represented by the dashed waveform, can be calculated using the I²T formula. This accumulated variable Va dissipates over time after the initial time. Furthermore, since the clamping time interval in Figure 7A is sufficient to release the current accumulation circuit, it can continue operating at this clamping frequency without triggering over-cycle protection. Conversely, referring to Figure 7B, when the excess current Ier is 10A, the accumulated variable Va, represented by the dashed waveform, can also be calculated using the I²T formula. This accumulated variable Va also dissipates over time after the initial time. However, because the excess current Ier is larger, the accumulated variable Va is larger, thus prolonging the time it takes for the accumulated variable to dissipate. Furthermore, the clamping time interval in Figure 7B is insufficient to release the current accumulation circuit (not shown). Therefore, the accumulated variable Va is superimposed when the electric gripper 100 clamps again, causing the accumulated variable Va to exceed the accumulation threshold Vmax (e.g., but not limited to, 7A). As a result, the electric gripper 100 enters over-cycle protection and can issue a warning to prevent damage to the motor 2 that could shorten its service life.

[0059] Please refer to Figure 8, which is a flowchart of the operation method of the electric gripper disclosed herein, and refer to Figures 1-7B in conjunction. The operation method flowchart in Figure 8 is mainly used to control the electric gripper 100 to provide excess clamping force Fer. The operation method of the electric gripper 100 includes providing current to the motor of the electric gripper, and the motor providing torque according to the current to drive the transmission mechanism (S100). The structure of the transmission mechanism 3 can be referred to in conjunction with Figures 1 and 3 of this disclosure, and its applicable structure can be deduced by analogy, and is not limited to the structure of Figures 1 and 3. Then, the transmission mechanism drives the two-finger plate holder to move in the closing direction or the away direction (S200). The circuit board 1 can provide parameters such as voltage V, current I, and frequency f to control the rotation of the motor 2, so that the motor 2 can drive the transmission mechanism 3, thereby driving the two-finger plate holder 4 to move in a given direction in the forward direction (i.e., the two-finger plate holder 4 towards the closing direction) or in the reverse direction (i.e., the two-finger plate holder 4 towards the away direction). When the two-finger holder 4 moves in the closing direction, the electric gripper 100 can grip the object 200 by closing the two-finger holder 4. Conversely, when the two-finger holder 4 moves in the moving away direction, the electric gripper 100 can release the object 200 by moving the two-finger holder 4 away.

[0060] Then, when the two-finger holder moves, an excess current exceeding the rated current is supplied to the motor at the first moment (S300). When the two-finger holder 4 begins to move in the closing direction to clamp the object 200 (i.e., at the first moment), the electric gripper 100 of this disclosure controls the drive circuit to supply an excess current Ier to the motor 2 according to an external control signal. Then, the motor provides excess torque based on the excess current to drive the transmission mechanism, thereby controlling the closing of the two-finger holder through the transmission mechanism to provide an excess clamping force to clamp the object (S400). Finally, the clamping force of the two-finger holder is maintained within a specific range whose upper limit is the excess clamping force by the transmission mechanism (S500). When the two-finger gripper 4 clamps the object 200 and the electric gripper 100 displaces to the appropriate position to release the two-finger gripper 4 (i.e., at the second time), the transmission mechanism 3 can maintain the clamping force of the two-finger gripper 4 within a specific range (e.g., but not limited to, 30% below the excess clamping force Fer) through mechanical actuation. In this disclosure, the transmission mechanism 3 can be structurally designed to have a self-locking function, giving the gripper 4 an irreversible self-locking characteristic after displacement. It is worth mentioning that, in one embodiment, the detailed operation method and detailed implementation method of the electric gripper 100 not shown in FIG8 can be referred to in conjunction with the relevant descriptions in FIG1-7B, and will not be described in detail here.

[0061] However, the above description is only a detailed description and drawings of preferred embodiments of the present invention. However, the features of the present invention are not limited thereto and are not intended to limit the present invention. The scope of the present invention should be determined by the following claims. All embodiments that are in line with the spirit of the claims and similar variations thereof should be included in the scope of the present invention. Any variations or modifications that can be easily conceived by those skilled in the art within the field of the present invention can be covered by the following claims. [Simplified Explanation of the Diagram]

[0010] Figure 1 is a structural schematic diagram of the first embodiment of the electric gripper disclosed herein;

[0011] Figure 2A is a schematic diagram of the principle of the lead angle disclosed herein;

[0012] Figure 2B is a schematic diagram of the principle of frictional resistance disclosed herein;

[0013] Figure 2C is a schematic diagram of the principle of the self-locking capability disclosed herein;

[0014] Figure 3 is a structural schematic diagram of the second embodiment of the electric gripper disclosed herein;

[0015] Figure 4A is a waveform diagram of the first embodiment of the motor current disclosed herein;

[0016] Figure 4B is a schematic diagram of the clamping force curve of the motor current in Figure 4A in this disclosure;

[0017] Figure 5A is a waveform diagram of the second embodiment of the motor current disclosed herein;

[0018] Figure 5B is a schematic diagram of the clamping force curve of the motor current in Figure 5A applied in this disclosure;

[0019] Figure 6A is a graph of instantaneous current versus running time disclosed in this invention;

[0020] Figure 6B is a schematic diagram of the configuration of the heating element disclosed herein;

[0021] Figure 7A is a waveform diagram of the first operating mode of the overcurrent protection mechanism disclosed herein;

[0022] Figure 7B is a waveform diagram of the second operating mode of the overcurrent protection mechanism disclosed herein; and

[0023] Figure 8 is a flowchart of the operation method of the electric gripper disclosed herein.

Claims

1. An electric gripper for gripping an object, wherein the electric gripper comprises: A circuit board for providing an excess current exceeding a rated current at a first moment; A motor, coupled to the circuit board to receive the excess current, and the motor is used to provide an excess torque according to the excess current; and a transmission mechanism, including: a gear set connected to the motor; a screw assembly including a rod body, the two ends of which respectively form a left-hand thread and a right-hand thread helical towards the center of the rod body, and the motor is used to drive the gear set through the excess torque to control the rotation of the rod body; and a linear slide rail disposed on one side of the screw assembly; and a two-finger holder, respectively screwed to the left-hand thread and the right-hand thread, and engaged with the linear slide rail, so as to reciprocate on the linear slide rail according to the rotation of the rod body; wherein, the motor is used to drive the two-finger holder to move in the closing direction through the excess torque, so as to provide an excess clamping force to clamp the object through the closing of the two-finger holder, and at a second time after clamping the object, the transmission mechanism maintains the clamping force of the two-finger holder within a specific range with an upper limit value of the excess clamping force.

2. The electric gripper as described in claim 1, wherein the left thread and the right thread have a lead angle, and the two-finger holder has a frictional resistance with the left thread and the right thread respectively; wherein, The lead angle is below a certain angle and the frictional resistance is above a certain resistance, so as to provide a self-locking function at the second time to maintain the clamping force of the two-finger plate seat within the specific range.

3. The electric gripper as described in claim 2, wherein the transmission mechanism further includes: An unlocking knob is used to rotate the rod to release the self-locking function and release the clamping force of the two-finger plate seat.

4. The electric gripper as described in claim 1 further includes: A position sensing circuit is configured on the circuit board and is used to sense the position of a rotor of the motor and provide a position signal; wherein, at the second time, the motor provides a torque based on a current lower than the rated current, and the circuit board determines whether the rotor has been displaced based on the position signal.

5. The electric gripper as described in claim 1 further includes: A current detection circuit is configured on the circuit board and is used to sense the excess current in the first time; wherein the circuit board calculates a duration of the first time based on the excess current, and when the circuit board determines that the duration is higher than a time threshold, the electric gripper enters an overcurrent protection.

6. The electric gripper as described in claim 1 further includes: A temperature sensing circuit is configured on the circuit board and is used to sense an ambient temperature of the circuit board; wherein, when the circuit board determines that the ambient temperature is higher than a temperature threshold, the electric gripper enters an over-temperature protection mode.

7. The electric gripper as described in claim 1 further includes: A current accumulation circuit is configured on the circuit board, and an accumulation variable is calculated based on the excess current and the first time; wherein, when the circuit board determines that the accumulation variable is higher than an accumulation threshold, the electric gripper enters an over-cycle protection.

8. An electric gripper for gripping an object, wherein the electric gripper comprises: A circuit board for providing an excess current exceeding a rated current at a first moment; A motor, coupled to the circuit board to receive the excess current, and the motor is used to provide an excess torque according to the excess current; and a transmission mechanism, including: a gear set connected to the motor; and a meshing transmission mechanism connected to the gear set, wherein the motor drives the gear set through the excess torque to control the meshing transmission mechanism to rotate in a direction perpendicular to an output shaft of the gear set; two-finger holders, each including a toothed row, and the toothed rows of the two-finger holders reciprocate accordingly according to the rotation of the meshing transmission mechanism; wherein the motor is used to drive the two-finger holders to move in a closing direction through the excess torque, so as to provide an excess clamping force to clamp the object through the closing of the two-finger holders, and at a second time after clamping the object, the meshing transmission mechanism maintains the clamping force of the two-finger holders within a specific range with an upper limit value of the excess clamping force.

9. The electric gripper as described in claim 8, wherein the engagement transmission mechanism comprises: A worm gear includes a rod body forming a first thread in a specific direction; and a worm wheel including a second thread, the worm wheel being perpendicular to the axis of the worm gear and rotating along the vertical direction of the output shaft by being screwed into the first thread through the second thread; wherein the first thread has a lead angle, and there is a frictional resistance between the first thread and the second thread; the lead angle is below a specific angle, and the frictional resistance is above a specific resistance, so as to provide a self-locking function at the second time to maintain the clamping force of the two-finger holder within the specific range.

10. The electric gripper as described in claim 8 further includes: A current accumulation circuit is configured on the circuit board, and an accumulation variable is calculated based on the excess current and the first time; wherein, when the circuit board determines that the accumulation variable is higher than an accumulation threshold, the electric gripper enters an over-cycle protection.

11. A method of operating an electric gripper for controlling the electric gripper to clamp an object, the method of operating the electric gripper comprising the following steps: (a) providing a current to a motor of the electric gripper, and the motor providing a torque according to the current to drive a transmission mechanism via the torque; (b) the transmission mechanism driving a two-finger holder to move in a closing direction or a moving away direction; (c) when the two-finger holder is moving, providing an excess current exceeding a rated current to the motor at a first moment; (d) the motor providing an excess torque according to the excess current to drive the transmission mechanism to control the closing of the two-finger holder and provide an excess clamping force to clamp the object via the transmission mechanism; and (e) maintaining the clamping force of the two-finger holder within a specific range with an upper limit of the excess clamping force via the transmission mechanism.

12. The method of operating the electric gripper as described in claim 11 further includes the following steps: At the first moment, the motor increases the excess clamping force by adjusting the excess torque.

13. The method of operating the electric gripper as described in claim 11 further includes the following steps: At the first moment, the motor increases the excess gripping force by increasing its rotational speed.

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