Delta robots are relatively small robots employed in handling food items for packaging, pharmaceuticals for casing, and electronics for assembly. The robots’ precision and high speed make them ideally suited to these applications. Their parallel kinematics enables this fast and accurate motion while giving them a spiderlike appearance that’s quite different from that of articulated-arm robots. Delta robots are usually (though not always) ceiling mounted to tend moving assembly and packaging lines from above. They have a much smaller working volume than an articulated arm, and very limited ability to access confined spaces. That said, their stiffness and repeatability are assets in high-precision processing of delicate workpieces — including semiconductors being assembled. Delta robots in context Industrial robots are broadly categorized as mobile robots, serial manipulators, or parallel manipulators. Mobile robots include autonomous ground vehicles (AGVs) and automated forklifts that are primarily programmed to move materials around factories and warehouses. Robots classified as serial manipulators have a chain of kinematic linkages connecting a fixed base to an end effector; these robotics include articulated arms
Figure 2: A delta robot is a type of parallel manipulator with three parallelograms all connected to a single rigid body at the end effector end. The base of each parallelogram is actuated in a single degree of freedom relative to the robot’s base. Delta robots are typically ceiling mounted to tend conveyors or workpieces from above. (Image source: Wikimedia Commons)
and cartesian robots. Because the rigidity and positional accuracy of each linkage is dependent on the previous linkage, serial manipulators are decreasingly accurate and rigid the further the linkage is from the base. Though there are exceptions, this morphology tends to limit the accuracy of six-axis robots to a few millimeters … and after rapidly moving to a new position and stopping, such robots’ end effectors will oscillate for some time before settling. One type of serial manipulator use in many of the same applications as delta robots is the selective compliance articulated robot arm or SCARA robot. They’re mechanically quite simple with
two revolute joints aligned so that their axes are parallel to each other and a third linear axis. The two revolute joints provide X-Y positioning in a single plane while the third linear axis provides motion in the Z direction. While they can lack the precision of delta robots, SCARAs are relatively low cost and can execute tasks quite rapidly — even in confined spaces. In contrast with serial manipulators, robots classified as parallel manipulators (including delta robots) have multiple kinematic linkages connecting the end effector to the base. Such morphology makes for a much stronger, stiffer, and lighter structure than serial robot types. Their lightweight yet rigid
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