This page provides an detailed overview about the Pneumatic Small Gripper Kit (PSG).

Contents

• Contents
• Overview
• Hardware
• Software
• Applications
• User Guide
• Technical Specifications
• Kit Components
• Technical Drawings
• Sensor Adjustment Instructions
• Maintenance

Overview

Assembling, configuring, and troubleshooting a ClickSmart gripper is easy once a few basic concepts are understood. The picture-based User Guides are meant as a quick easy reference to assemble the hardware. This document is meant to be a supplement to that and to explain the entire concept of how and why things work the way they do. There are two aspects of setting up a ClickSmart gripper; hardware and software, which are interrelated and play an important role in the operation of the gripper.

Hardware

Air Valves

All ClickSmart grippers use the same 5/2-way (5 ports and 2 positions), single solenoid, pneumatic valve. The large grippers have one, and the small grippers have two each. This valve has 1 port for the supply air, 2 output ports, and 2 exhaust ports. There is a pneumatic fitting on the supply and output ports, and the exhaust ports do not have any fittings. The valve has two different states. The first state is with one of the output ports open (sending positive air pressure) and with one closed (no air pressure). The second state is the opposite, with the first port closed and the second one open. All the valve does is switch between these two states. One of the outputs is tied to the open gripper position, and the other is tied to the closed gripper position. This means that the fingers will be forced open in one state and forced closed in the other state.

One of the two states is the “normal” state, which means the state of the valve when there is no power to it. The port that is open in the normal state is referred to as “normally open” and the one that is closed in the normal state is “normally closed”. This is important because if the arm loses power, including during an emergency stop, the valve will revert to the normal state. You may want to configure the gripper such that it is in the gripping position in the normal state so that if it is holding a part when it loses power, it will not drop it. In addition, knowing how the air is plumbed from the valve is necessary when configuring the signals.

Note: One of the ports is labelled with a "P". This is the normally open output. Do not let it confuse you since "P" sometimes stands for pressurized, meaning the input. 

When connecting the valve to the gripper with the air hoses, keep in mind which valve is going to which position. If you want the fingers to be closed when there is no power, make sure to connect the normally open port on the valve to the closed input on the gripper.

Proximity Sensors

There are two proximity sensors on each gripper. One of the sensors should be 'on' when the fingers are open all the way (and 'off' when in any other position), and the other should be 'on' when the fingers are closed all the way (and 'off' in any other position). If this is not the case, then use the very small hex key to loosen, then slide the sensors to the correct position, then tighten again so they do not move. The wire connected to each sensor is labeled indicating to which input it is connected. The default software settings use the sensor labeled “1” to indicate the open position and the sensor labeled as “2” as the closed position. If the physical sensors are set up in the opposite manner, this can be changed in the software. Make note of which number sensor is the open position and which is the closed position.

The image above shows the Pneumatic Large Gripper (PLG). The Pneumatic Small Gripper (PSG) is the same, except doubled using the other port on the ClickSmart Plate.

Software

After connecting the ClickSmart to the robot, you will need to open the tooling gallery to configure the gripper. Enter a name, its mass, tool center point offsets, and estimated center of mass. Scroll down and select “Gripper” as the tool type. After saving, the gripper should work, but maybe not as expected, especially when using train-by-demonstration. This is because the signals need to be configured to match the hardware configuration and expected behavior.

Let’s assume you are gripping a part from the outside, in other words, when the fingers close, it grips the part. This is most common, but there are situations in which the gripper opens to grip a part. Let’s also assume that you want the “normal” state of the gripper to be closed (which in this case means gripping) so the robot doesn’t drop a part when it loses power.

Because training a task in Intera Studio is so flexible, you are free to configure the signals any way you like, then use the correct combination outputs and inputs to achieve the desired behavior. However, the templates and train-by-demonstration on the robot make the following assumptions:

• Outputs
  • Power: On
  • Grip:
    • True: grasp the part
    • False: release the part
• Inputs
  • Open:
    • True: the fingers are all the way opened, and not grasping a part
    • False: the fingers are not all the way opened
  • Close:
    • True: the fingers are all the way closed, and not grasping a part
    • False: the fingers are not all the way closed

When both open and closed are false, the fingers are neither all the way open, nor all the way closed. This must mean the gripper is grasping a part.

Note that there are 2 sets of the same signals, designated as A and B. This refers to the connector on the ClickSmart plate to which the cable is connected. The large gripper uses only one port while the small gripper uses both both ports since there are 2 sets of actuators.

Output Signals

Power - This controls whether the 24V to the proximity sensors is on or off. This should be configured so it is on all the time, which the default values should do.

• Port: A_out1 (or B_out1)
• Default: true
• Inverted: off

Grip - This is the signal to the pneumatic valve that tells it which state to be in. No signal means it is in the “normal” state. If you connected the normally open port on the valve to the close fingers port on the gripper, the fingers will be closed when this signal is low. The reverse is true; when the signal is high, the fingers will open. Setting the grip signal in software to ‘false’ typically means the electrical signal is low, and setting grip to ‘true’ typically means the electrical signal is high. So, this results in ‘false’ = grip the part, and ‘true’ = release the part. This is a problem because the train-by-demonstration functionality assumes the opposite. To fix this, we enable “invert signal” to flip this logic (this is the default position). This will make it so that setting grip to ‘true’ sets the signal low (de-energizing the solenoid, returning the valve to the normal state) and closes the fingers, and setting grip to ‘false’ sets the signal high (energizing the solenoid, switching the valve) and opening the fingers.

• Port: A_out2 (or B_out2).
• Default: This will be the state of the gripper when a task is reset. It is often expected that the task will start with an open gripper. If this is the desired behavior, make this ‘false’. Making this ‘true’ will ensure the gripper doesn’t drop a part if the task is reset, however a command to open the gripper before the first pick will be required in the behavior tree.
• Invert signal: ‘On’ if the hardware is connected as described above. Test to make sure that that true = grip and false = release. If not, toggle this setting.

Input Signals

Open - This is the input signal indicating the fingers are in the open position. Make sure the open position sensor and the software configuration of the port for the signal match. By default in software, this is tied to A_in1 (or B_in1) which means it is connected the wire labeled “1”. The sensors are also pre-set in this position on the hardware.

• Port: A_in1 (or B_in1). This is the default hardware setup, but it is possible to change.
• Default: Since this is an input, it shouldn’t matter what the default setting is. However, if using version 5.1 or earlier, set this to false due to a software issue which was resolved in 5.2.
• Invert signal: ‘On’

Closed - This is the signal indicating the fingers are in the closed position. Make sure the closed position sensor and the software configuration of the port for the signal match. By default in software, this is tied to A_in2 (or B_in2) which means it is connected the wire labeled “2”. The sensors are also pre-set in this position on the hardware.

• Port: A_in2 (or B_in2). This is the default hardware setup, but it is possible to change.
• Default: Since this is an input, it shouldn’t matter what the default setting is. However, if using version 5.1 or earlier, set this to false due to a software issue which was resolved in 5.2.
• Invert signal: ‘On’

After saving the configuration of the signals, open up Shared Data to make sure the signals are working correctly. Find the input and output signals for the gripper.

• With the air turned off, move the fingers back and forth from the fully open position to the halfway position and make sure the value of the “open” signal toggles correctly. Then move the fingers from the fully closed position to the halfway position, and make sure the “closed” signal changes correctly.
• Turn the air on and toggle the value of the “grip” signal and make sure the fingers grasp when it is ‘true’ and release when it is ‘false’.
• Make the ClickSmart gripper the active tool center point in the task, then press and hold the oblong white button on the cuff of the robot. This should toggle the gripper open and closed with each press and hold.