By Will Charpentier
Updated Mar 24, 2022
When you compare the human arm to a robotic counterpart, the differences become clear: a human uses chemical muscle fibers and bone, whereas a robotic arm relies on hydraulics or electromechanics to generate force. Both systems share a common architecture— a rigid frame that moves through push/pull leverage and a terminal manipulator that grips or releases objects.
Weld the manipulator stator (a flat aluminum sheet) to the lower end of the forearm aluminum beam that lacks a ram attachment link. Attach a unidirectional robotic hinge joint to this point, then connect the trapezoidal mobile block of aluminum to the joint so the ram attachment link sits on top. Close the hinge so the stator and mobile parts of the manipulator are sealed.
Form the elbow by welding the upper and lower arm segments together at a hinge. Mount an additional hinge between the upper arm and the external shoulder support to allow vertical articulation.
Secure the piston of a hydraulic ram to the attachment link on the mobile manipulator. With the ram fully extended, weld it to the forearm beam, ensuring a tight seal for fluid transfer.
Attach hydraulic rams to the attachment links on both the upper arm and forearm beams. When the forearm is fully extended and the corresponding ram is fully compressed, weld the forearm ram to the upper arm. Repeat the process for the upper arm and the external shoulder support, completing the three‑link kinematic chain.
Route hydraulic hoses from each ram to the appropriate ports on the hydraulic manifold. Connect the bidirectional hydraulic motor, reservoir, and control valve to the manifold, creating a closed hydraulic circuit.
Set the control valve to the closed position and prime the system with hydraulic fluid until the reservoir reaches the specified level. To open the manipulator, activate the valve to compress the ram piston; the rearward motion pulls the mobile side of the manipulator upward, opening the hand. To close the hand, fully extend the piston, pushing the mobile portion forward.
The direction of the hydraulic piston controls the robotic arm’s movement. Think of the piston as a door handle: push to close, pull to open.
Hydraulic systems operate under high pressure and can be hazardous. Follow all safety protocols and wear appropriate personal protective equipment.
