The Robotic Arm
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flagWhat you'll discover
- arrow_forwardControl base, shoulder and elbow joints to position a gripper
- arrow_forwardCount the degrees of freedom of the arm
- arrow_forwardGrab and release a ball by combining joint moves
- arrow_forwardExplain forward kinematics in one sentence
Joints and degrees of freedom
Every independent way a robot can move is called a degree of freedom, or DOF. This arm has three: the base spins left-right, the shoulder tilts up-down, and the elbow bends. The gripper opening is a bonus mover, but it positions nothing — so we say the arm itself has 3 DOF.
Your own arm has seven degrees of freedom from shoulder to wrist, which is why you can scratch your back in ways no simple robot can.
Forward kinematics
Forward kinematics answers one question: given every joint angle, where exactly is the gripper tip? The math chains together: the base angle rotates everything, the shoulder angle tilts the upper arm, the elbow angle bends the forearm, and adding it all up gives one point in space.
When you move the sliders, the simulation is computing forward kinematics live, every single frame, to draw the arm correctly.
The art of grabbing
Grabbing looks easy but is famously hard in robotics. The gripper must arrive close enough to the ball, be open before contact, and close at the right moment with the right force — too soft and the ball slips, too hard and it gets crushed.
In the simulation, the rule is simple: if the gripper tip is near the ball when you close it, the grab succeeds. Real factory robots add force sensors in their fingers to feel exactly this moment.
Arms that build our world
Industrial robotic arms weld cars, pack medicine, assemble phones and even perform surgery. A typical factory arm has six joints, repeats its motion thousands of times a day, and places parts with accuracy finer than a human hair.
Hospitals in Nepal have begun using surgical-assist technology too, and engineering students at universities like Pulchowk Campus build and program arms much like this one as semester projects.