Robotlab - Piab Vacuum Kit

Version 1

Piab provides vacuum technologies for lifting and moving objects in automation applications. The lab space has received a package of vacuum cups and soft grippers that may suit different payloads and object geometries. The grippers can be connected to robot arms such as UR5e and actuated with vacuum ejector (the red aspirator in the picture) or piCOMPACT I/O link (the device in the picture). Note you would need air compressor as in the picture below and pneumatic solenoid valves to control on/off of the grip. Consult the lab manager on how to use them properly.

The lab has sufficient gadgets to build circuits to control the air flow and hence the on/off of grip from a computer. As a demonstrated example, you may find a setup in a plastic box using Aruidno, power control and valves to do so.

Note that the valves is drive by 12V power so we cannot directly connect them to the output pins of Arduino (some motor control boards might be fine though). The power control here serves as a switch that allows us to use small electric currents to signal on/off of larger currents.

We can use serial port to communicate with Arduino to trigger the on/off action. On the arduino side, we may simply use a code snippet:

const int airvalvePin = 8;
int commandByte;

void setup(){
    Serial.begin(9600);
    pinModel(airvalvePin, OUTPUT);
}

void loop(){
    if(Serial.available() > 0){
        commandByte = Serial.read();

        if(commandByte == 'O' || commandByte == 'o'){
            digitalWrite(airvalvePin, HIGH);
        }
        if(commandByte == 'C' || commandByte == 'c'){
            digitalWrite(airvalvePin, LOW);
        }
    }
}

While on the computer side, we can use python to write to the serial port:

import serial
import time

ser = serial.Serial('/dev/ttyACM0', 9600)   #check the port identifier on your computer
time.sleep(1)

while True:
    try:
        cmd = input("Input O or C to open or close the valve...")
        if len(cmd) > 0:
            ser.write(str.encode(cmd[0]))
    except KeyboardInterrupt:
        print("Exit the loop and close the serial.")
        break

ser.close()

A good practice could be wrap the serial communication into a grip() function. Note that valve-on means closing the gripper or activating the suction since the compressed air is used to create vacuum. You might want to name the command differently if that creates confusion.

Version 2

The new version of the setup use a 6-channel piCOMPACTx10 and is actuated by the digital output of the robot arm UR5e. This makes it suitable for controlling robot and pump form the same digital interface. The following code cyclicly switches the pump ON and OFF for a defined amount of cycles, with an interval of 2 seconds. The standard digital output pin decides the direction of the air flow.

import rtde_io
import rtde_receive
import time

IP="ROBOT_IP"
_io = rtde_io.RTDEIOInterface(IP)
_r = rtde_receive.RTDEReceiveInterface(IP)

to_psi= lambda V:(V-4/5)*101/2 # linear relationship between voltage and pressure 
pressure=[]
voltage=[]

def wait_and_log(seconds):
    counter=0
    step=0.01
    while counter<seconds: 
        voltage.append(_r.getStandardAnalogInput0()) #read voltage
        pressure.append(to_psi(_r.getStandardAnalogInput0())) #convert to pressure
        time.sleep(step)
        counter+=step

def print_pin_state(pin):
    # Get the state of the pin
    state = _r.getDigitalOutState(pin)
    if state:
        print(f"Pin {pin} is HIGH")
    else:
        print(f"Pin {pin} is LOW")


#Chose the pin of the standard digital output
mode="suck"
if mode=="blow":
    pin=0
elif mode=="suck":
    pin=1
else:
    print("Invalid mode. Use 'blow' or 'suck'.")

seconds=2
counter=0
while counter<10:# ten on off cycles
    _io.setStandardDigitalOut(pin, True) #start

    wait_and_log(seconds)

    _io.setStandardDigitalOut(pin, False)#stop

    wait_and_log(seconds)
    counter+=1