JP6472136B2 - Mass measuring device - Google Patents

Description

  The present invention relates to zero adjustment of a mass measuring device that detects the mass of an article while the speed of the article is changing.

  In spring balances and electronic balances, the mass is measured while the article is stationary in order to eliminate the influence of acceleration other than gravitational acceleration. However, recently, the opportunity to move an article with a robot hand increases, and accordingly, there is a demand for measuring the mass of the article while moving the article and using it for post-processing.

  In order to meet this requirement, the applicant has developed a series of mass measuring devices as disclosed in the following patent documents. This mass measuring device is based on measuring the mass of an article from the force and acceleration acting on the article while the speed of the article is changing.

JP2013-079931A JP 2013-174503 A JP 2013-174570 A JP 2013-185846 A JP 2013-185847 A JP 2013-185848 A JP 2013-195197 A JP 2013-195200 A

  This mass measuring apparatus includes a force sensor that detects a force acting on an article, a robot hand that grips the article, a robot arm that moves the article while accelerating, and an acceleration sensor that detects an acceleration acting on the article. It is a thing. The force sensor used here is a strain gauge type load cell that converts the mechanical strain into an electrical signal and outputs it. If the robot hand hits something during use and an impact is applied to the force sensor, the zero point Will shift. Further, there is a problem that the zero point shifts due to repeated use or due to a change in ambient temperature.

  Such a zero point change can be resolved by operating the “zero key” described later before the start of operation. However, since this device measures the mass of an article during movement, such operation is performed during operation. There was a problem that could not.

  The present invention is intended to solve the problems peculiar to the mass measuring device incorporated in such a robot arm, and is easy to use because it can automatically adjust the zero point of the force sensor and maintain the weighing accuracy. It is an object to provide a mass measuring device.

The mass measuring device according to the present invention is a mass measuring device that measures the mass of an article from the force and acceleration acting on the moving article,
A force sensor for detecting a force acting on the article;
An acceleration sensor for detecting an acceleration acting on the article;
A control unit for inputting the output of each sensor,
The control unit automatically updates the output of the force sensor as a zero point when the output of the force sensor is unloaded and the output of the acceleration sensor is zero.

  In the case of a robot arm incorporated in a production line, there is a time zone to wait until the next article is sent even during operation. The control unit finds such a time zone from the output of each sensor, and automatically updates the zero point of the force sensor when the output of the force sensor is unloaded. Thereby, it is not necessary to forcibly stop the robot arm during operation and perform zero point adjustment, so that the weighing accuracy can be kept constant even during continuous operation.

  In addition, the control unit automatically updates the output of the force sensor as a zero point when a no-load state of the force sensor continues for a predetermined time. For example, since this type of sensor output is output through a filter, a certain delay time occurs with respect to the input. Therefore, if the delay time elapses and it is confirmed that the output of the force sensor is in an unloaded state by a plurality of subsequent samplings, the average value of the sampling data input at that time is automatically updated as a zero point. It is. This makes it possible to update the zero point more reliably.

  In addition, the control unit inputs a signal from a controller that controls movement of the acceleration sensor instead of the output of the acceleration sensor, and when the output of the acceleration sensor can be regarded as zero by that time, then The output of the force sensor is automatically updated with the zero point as a zero point.

  For example, even if the robot arm is stopped, if a spring system is interposed between the acceleration sensor and the robot arm, the acceleration sensor detects the acceleration caused by the vibration of the spring system until the robot arm stops. However, the force sensor can remove such vibrations with a filter, so if it receives a stop signal from the controller and the unloaded state of the force sensor continues for a predetermined time, the force sensor output is stored as a zero point. Update. Thereby, for example, even when the robot arm has finished a series of processes and is waiting for the next article, the zero point of the force sensor can be updated.

  According to the present invention, since it is not necessary to stop the robot arm during operation and perform zero adjustment of the force sensor, the measurement accuracy can be kept constant even during continuous operation. Therefore, an easy-to-use mass measuring device can be provided. In addition, when the control unit inputs a signal from the controller and the output of the acceleration sensor can be regarded as zero by that, the output of the force sensor is automatically updated as a zero point, so the robot arm finishes a series of processing. The zero point can be updated even in a short time zone waiting for the next article. Therefore, even if the robot is continuously operated, there is an effect that the measurement accuracy is not lowered.

1 is a schematic configuration diagram of a mass measuring device according to an embodiment of the present invention and a robot in which the mass measuring device is incorporated. FIG. The schematic block diagram of the robot hand which concerns on other embodiment. The block diagram of the configuration of the mass measuring device and the robot control system. An example of the flowchart which updates a zero point automatically.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following embodiments do not limit the technical scope of the present invention.

(1) Basic Configuration of Mass Measuring Device and Robot FIG. 1 shows a schematic configuration diagram of a mass measuring device 10 according to an embodiment of the present invention and a robot 20 in which the mass measuring device 10 is incorporated. In this figure, the mass measuring apparatus 10 includes a force sensor 11 that detects a force acting on a moving article Q, and an acceleration sensor 12 that detects an acceleration acting on the article Q. The robot 20 includes a robot arm 21 and a robot hand 22 that holds the article Q.

  For example, a strain gauge type load cell is used as the force sensor 11. In the strain gauge type load cell, the free end side is displaced relative to the fixed end side by the load of the article Q, thereby converting the mechanical strain generated in the load cell into an electric signal and outputting it as a loaded force. .

  As the acceleration sensor 12, for example, any one of a MEMS type small acceleration sensor and a general commercially available acceleration sensor is appropriately employed in addition to a strain gauge type load cell. The acceleration sensor 12 and the robot hand 22 are attached to the free end side of the force sensor 11.

  The robot arm 21 moves the robot hand 22 three-dimensionally, and one end of the force sensor 11 is fixed to the distal end portion 23 thereof. As this robot arm 21, for example, an articulated robot, a parallel link robot, or the like can be adopted.

  The robot hand 22 grips the article Q, and the robot hand 22 in FIG. 1 shows an example of a finger type driven by a motor, but instead of this, the article Q is subjected to negative pressure as shown in FIG. An air adsorbing type that adsorbs and holds can be used. The finger type of FIG. 1 is suitable when the article Q is a solid material, and the air adsorption type of FIG. 2 is suitable when the shape is not constant, such as a bag-packed product.

  FIG. 2 shows a schematic configuration diagram of this air adsorption type. In this type, a bellows-like suction pad P made of silicon rubber is attached to an aluminum box B so that the suction pad P communicates with the inside of the box B. By holding the inside of the aluminum box B at a negative pressure, the articles Q are sucked and held by the suction pads P. In addition, since a plurality of articles Q may be simultaneously held by a large number of suction pads P, the number, shape, arrangement, etc. of the suction pads are appropriately changed according to the type of the articles Q. Therefore, a plurality of types of robot hands 22 are prepared according to the type of the article Q, and these are used properly according to the type of the article Q.

(2) Basic Configuration of Control System FIG. 3 shows a block diagram of the configuration of the control system of the mass measuring apparatus 10 according to one embodiment and the robot 20 in which it is incorporated. In this figure, the force sensor 11 and the acceleration sensor 12 of the mass measuring apparatus 10 are electrically connected to the control unit 30, and the force acting on the article Q is input from the force sensor 11 to the control unit 30 as a detection signal. From the acceleration sensor 12, the acceleration acting on the article Q is input to the control unit 30 as a detection signal. The control unit 30 is configured by a computer, and implements various functions described later by reading and executing various programs stored in the storage unit 31. In addition, an operation display unit 13 is connected to the control unit 30.

  The operation display unit 13 is used to set various parameters necessary for mass measurement and to start and stop the operation of the robot 20. Specifically, it is configured by a keyboard, a touch panel, and the like, and the types of keys are not shown, but in addition to numeric keys, a “span key” described later and a “first zero key” operated during movement are provided. And a “second zero key” operated while still.

The control part 30 calculates | requires the mass of the articles | goods Q in which the speed is changing from the following formula by executing a program.
m = S {(Fm / Fa)-(Fmz / Faz)}
Here, S is a span coefficient. Fm is the output of the force sensor 11 when moving the article Q of mass m, and Fa is the output of the acceleration sensor 12 at that time. Fmz is an output of the force sensor 11 when the robot hand 22 is moved in an unloaded state, and Faz is an output of the acceleration sensor 12 at that time.

The span coefficient S is a coefficient represented by the following relational expression.
S = ms / {(Fms / Fas)-(Fmz / Faz)}
Here, ms is the mass of the span weight, Fms is the output of the force sensor 11 when the robot hand 22 lifts the span weight, and Fas is the output of the acceleration sensor 12 at that time. Fmz and Faz are the output of the force sensor 11 when the robot hand 22 is moved with no load, and the output of the acceleration sensor 12 at that time, as described above.

These span coefficients S and output ratios (Fmz / Faz) are set and registered by the following operations in the initial setting.
First, prepare a span weight of mass ms, and then press the “Span key”. Then, the robot hand 22 lifts and lowers the span weight of mass ms. Meanwhile, since Fms is output from the force sensor 11 and Fas is output from the acceleration sensor 12, the control unit 30 stores the output ratio (Fms / Fas) at that time in the storage unit 31.
Subsequently, the “first zero key” is pressed. Then, the robot hand 22 moves up and down without anything, that is, in a no-load state. Meanwhile, Fmz is output from the force sensor 11 and Faz is output from the acceleration sensor 12. Therefore, the control unit 30 stores the output ratio (Fmz / Faz) in the storage unit 31.

  On the other hand, the “second zero key” stores the initial load of the force sensor 11, that is, the sum of the mass of the robot hand 22 loaded on the force sensor 11 and the mass of the acceleration sensor 12 as a zero point. If the “second zero key” is operated without holding anything, the output (initial load) of the stationary force sensor 11 is stored as a zero point. This zero point is basically a value that does not change, but when the robot hand 22 hits an object and an impact is applied to the force sensor 11, the zero point is shifted. Also, the zero point is shifted when the ambient temperature changes. The control unit 30 cancels such an offset amount by automatically updating the zero point.

  During operation, the outputs of the sensors 11 and 12 are always input to the control unit 30. When the control unit 30 determines that the output of the force sensor 11 is within the range of the no-load state and the output of the acceleration sensor 12 is also zero, the control unit 30 sets the output of the force sensor 11 at that time to the zero point. Is automatically updated. Thereby, even if the zero point changes, the offset amount is canceled, so the measurement error is eliminated.

  Further, in such automatic update, if the output of the force sensor 11 becomes no load, the zero point may be updated immediately. However, in order to perform the control more carefully, the delay time by the digital filter has elapsed. If it can be confirmed that the output of the force sensor 11 is maintained in the no-load state by sampling a plurality of times, the average value of the sampling data input at that time is automatically updated as a zero point. Thereby, more reliable zero update is performed.

  Further, when the control unit 30 receives a stop signal from the robot controller 24 described later, the output of the force sensor 11 is unloaded, and the unloaded state continues for a predetermined time after receiving the stop signal. If it can be confirmed, the output of the force sensor 11 at that time is automatically updated as a zero point. Thereby, for example, the zero point can be updated even in a short time when the robot arm 21 tries to release the article Q and return to the original position.

  In addition to the various programs executed by the control unit 30, the storage unit 31 stores the initially set span coefficient S, the zero as the initial load, the automatically updated zero, the calculated mass of the article Q, and the like. Remember.

  On the other hand, the robot controller 24 is configured by a computer, and the robot arm 21 and the robot hand 22 are electrically connected thereto. Further, an imaging device (not shown) is also connected. When the built-in program is executed, the robot arm 21 and the robot hand 22 are driven and controlled, and the article Q is lifted or moved while the position of the article Q is confirmed by the imaging device. ing.

  Further, the robot controller 24 and the control unit 30 are electrically connected via the communication cable 40, and when the mass of the lifted article Q is obtained, it is transmitted to the robot controller 24. If the robot 20 determines that it is a defective product that does not satisfy the reference value based on its mass, the robot 20 discharges it out of the line, and if it determines that the product is a positive product, moves it to a specified location. During such an operation, for example, when the robot arm 21 is stopped for a short period of time in order to wait for the arrival of the next article Q or to return to the original position, the controller 24 sends a stop signal at that timing. Is output to the control unit 30. Based on this, the control unit 30 determines whether or not to enter the above-described automatic zero update.

Next, the basic operation of the control unit 30 will be described based on the flowchart shown in FIG.
In operation, first, the above-described initial setting is performed (step S1). As a result, the span coefficient S and the zero points (Fmz, Faz) during movement of the sensors 11 and 12 are stored in the storage unit 31. Subsequently, the start button is pressed to start the operation of the robot 20. Then, the control part 30 inputs the output of each sensor 11 and 12 periodically, and memorize | stores it (step S2). Subsequently, the control unit 30 checks whether or not the output of the force sensor 11 is in a stable state (step S3). The determination as to whether or not it is stable is made based on whether or not the output of the force sensor 11 shows the same value a predetermined number of times. If the state is stable, it is confirmed whether or not the timer is started in the next step S4. If unstable, the process proceeds to step S5 to determine whether or not the timer is reset. This timer checks whether or not the delay time of the digital filter has elapsed, and is composed of a soft timer.

  If the timer has not started in step S4, the soft timer is started in the next step S6, and then the process returns to the original step S2. When the timer has started, it is checked whether or not the timer has expired (step S7). As a result, if the time has not expired, the process returns to the original step S2, and if the time has expired, the timer is reset in the next step S8, and then the process proceeds to automatic zero update (step S9). This automatic update is a plurality of output values of the force sensor 11 input while the timer is operating, and averages them and stores and updates them as zero points.

  On the other hand, if the output of the force sensor 11 has changed by the time up or if it has changed from the beginning, it is checked in step S5 whether or not the timer has been reset. If not reset, the timer in operation is reset in the next step S10. If it has already been reset, the peak value of the output of each sensor 11, 12 is detected in the next step S11. If the peak value cannot be detected, the moving speed of the article Q is in the process of change, so the process returns to the original step S2 and waits for the peak value to appear. When the peak value is found again from step S2 to step S11, the mass m of the article Q is obtained from the above formula using the peak value.

  While repeating the above steps at the computer processing speed, the mass m of the article Q is obtained and the zero point is automatically updated.

  As mentioned above, although one Embodiment of this invention was described, this invention is not limited to this, Other embodiment is also employable. For example, a static weighing mode is newly added to the mass measuring device, and a dynamic weighing mode for obtaining the mass of an article based on the output of each moving sensor and a stationary weighing mode according to how the robot 20 is used. You may make it switch. In the static weighing mode, for example, if the robot hand 22 lifts the article Q and stops and the output of the force sensor 11 is stabilized, the mass of the article Q is detected from the output. Alternatively, the robot hand 22 is provided with a container and the fluid is supplied to the container. When the fluid in the container is stabilized, the mass of the fluid is obtained from the output of the force sensor 11. Then, when the mass of the article Q is obtained, it is replaced with the next article. Alternatively, the fluid is transferred to another container, and then a new article is supplied to the grasped container. Even in such a case, since the zero point of the force sensor is automatically updated during operation, more accurate weighing can be performed.

  According to the present invention, since the mass of an article can be measured more accurately while the article is moved by a robot hand, the invention can be used in the field of using an industrial robot.

Q article 10 mass measuring device 11 force sensor 12 acceleration sensor 20 robot
21 Robot arm 22 Robot hand 24 Robot controller 30 Control unit

Claims (6)

A mass measuring device that measures the mass of an article from the force and acceleration acting on the article while the speed of the article is changing,
A force sensor for detecting a force acting on the article;
An acceleration sensor for detecting an acceleration acting on the article;
And a control unit for receiving the output of the sensors,
The mass measuring apparatus , wherein the control unit automatically updates the output of the force sensor as a zero point when the output of the force sensor is unloaded and the output of the acceleration sensor is zero. Wherein, when the no-load state of the force sensor persists predetermined time, characterized by automatically updating the zero-point output of the force sensor, a mass measuring device according to claim 1. A mass measuring device that measures the mass of an article from the force and acceleration acting on the article while the speed of the article is changing,
A force sensor for detecting a force acting on the article;
An acceleration sensor for detecting an acceleration acting on the article;
A control unit for inputting the output of each sensor,
Wherein the control unit further receives a signal from a controller for controlling the movement of the pre-Symbol acceleration sensor, the output of the force sensor is unloaded, the output of the acceleration sensor by a signal from the controller is expected to zero when causing做is characterized by automatically updating the output of the force sensor at the time as a zero point, mass measuring device.   4. The mass measuring apparatus according to claim 1, wherein the control unit automatically updates an output of the force sensor from which vibration is removed by a filter as a zero point. 5.   Robot hand,
  The mass measuring device according to claim 1, further comprising: a robot arm to which the force sensor to which the robot hand and the acceleration sensor are attached is fixed. .   The mass measuring device according to claim 5, wherein the control unit automatically updates the output of the force sensor as a zero point in a no-load state where the robot hand has nothing.

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