PROGRAMMING AND TRAJECTORY PLANNING OF ROBOTS IN INDUSTRIAL ENVIRONMENT

Starting from a brief review about robotics and motion planning, the aim of my work was to program three ABB robots in a predefined industrial environment to perform pick and place tasks, trying to optimize them in terms of cycle time and of trajectories. In this specific case, we are discussing about the presence of three anthropomorphic robots, with 6 degrees of freedom able to guarantee the maximum possible dexterity used to pick and place objects of different types and weights. Articulated or anthropomorphic means that the shoulder has three revolute joints, the first one vertical and the other two horizontal and parallel. The structure is very similar to human body, with trunk, arm and forearm with a final wrist so it provides the best dexterity and this is why it is used in most of the industrial applications. Task space is a sort of sphere sector, even if there is no a direct correspondence between joint and Cartesian coordinates, but accuracy is not constant inside the task space. Particularly two of them are equal models of IRB4600, with a maximum capacity of 60 kg and are used to pick and place clutch’s mechanisms of a maximum weight of 8 kg, with a gripper of about 32 kg. The third one, instead, an IRB1200, is used to move rivets of few grams, so it is sufficient with a maximum capacity of 5 kg. They both provide a double gripper to optimize the cycle time in order to be able to match the specification of 15s. The system scenario is composed of 13 stations, positioned in space in a pre-determined way, through which vehicular clutches are balanced, tested and finally marked. Since the area in which robots move is not regular and there are many obstacles as machines, laser cabinet and manipulators, it was necessary to declare some additional point to allow the movement. Due to this fact, all the movements have been performed as linear through the instruction MoveL so that the minimum trajectory is followed. Moreover, since all the robots are equipped with a double gripper, it was necessary to declare two different tools and perform the movements with respect to one of them. Moreover, all of them have been configured to meet safety requirements both in hardware and software through the Safe Move and WZones functionalities. Particularly, the two IRB4600 provided both of them due to the critical position inside the line, so their work area has been delimited by the Safe Move, while their movements around the pick and place areas have been managed by the WZones. The third one instead, since it is smaller and placed in a non critical position, provides only the software functionality through which it has been limited while approaching the rived feeder and the manipulator. This way, thanks to the Safe Move, the robot cannot be moved, even manually, outside the declared area, guaranteeing the integrity of the machines and gates around it. From the software point of view, instead, the encumbrance signals are set by the WZones themselves: in fact, every time the robot comes inside a certain area, the encumbrance signal is set to 1, so the PLC knows that for example the movements of the machines are limited while the robot is in that area. Then, to preserve machines integrity, I have defined also upper limits that guarantee that the robot, even in manual mode, cannot reach that altitude, so the mechanic is preserved.