Mars Rover Robotic Arm Design

Design problem

A rover arm is a cantilever. Any weight added to the end-effector generates bending loads across the links and demands greater holding torque from the joints, scaling up the further the arm extends. The arm also has to fit its actuators, brackets and links into a package that can still move through a useful range without parts colliding.

Three core mechanical demands shaped the final layout:

• Reachability: the gripper has to cover the workspace a planetary rover needs, from a raised position down to the ground in front of the chassis.
• Payload capacity: each joint must support both the target sample and the cumulative mass of all downstream components when fully stretched out.
• Joint constraints: each joint's real range of motion is set by its brackets, servo bodies and neighbouring links, not by the servo's rated travel.

Mechanical layout

Modelled as a complete SolidWorks assembly, the manipulator forms a serial chain of revolute joints where every structural component is tailored to its specific motor.

• Base and turntable: a cylindrical housing on a wide mounting flange. Mounted above it, the turntable pivots the entire manipulator assembly. The wide footprint spreads the overturning moment from the extended arm into the mounting surface.
• Shoulder joint: a heavy-duty servo secured within a lateral bracket atop the turntable. The shoulder carries the moment of the entire arm plus the payload at the longest lever arm, so it gets the largest actuator.
• Elbow joint: another high-torque servo positioned at the upper end of the lower link to actuate the upper segment. It sees a shorter moment arm than the shoulder but still carries the forearm, wrist and gripper.
• Wrist: a small-profile servo nested directly inside the tip of the upper link. Little mass sits outboard of the wrist, so a small actuator is enough, and keeping it light reduces the load on the shoulder and elbow.
• Gripper: a pair of jaws linked by interlocking gears and powered by a single miniature servo. The gear coupling makes both jaws move together and stay symmetric about the centreline, so the gripper closes on the object's centre without a second actuator.

Motor dimensions progressively decrease from the base toward the end-effector. This is the standard way to size a serial arm: mass moved toward the tip is multiplied by every joint's moment arm, so the outboard joints are kept as light as possible.

Kinematic analysis

Once the assembly constraints were applied, the manipulator's movement was evaluated in two ways:

• Forward kinematics: each joint is driven through its range and the gripper position is tracked, which maps the reachable workspace and shows where links, brackets and servo bodies interfere.
• Inverse kinematics: defining a desired end-effector coordinate and calculating the required joint angles reveals both whether a target is within reach and the exact posture needed to get there.

Together these confirmed the arm's workspace, the usable range of each joint once interference is accounted for, and that the design is mechanically feasible before any parts are made.

Files

You can find the native SolidWorks files alongside an interactive, rotatable 3D STL model in Tawfiq's SolidWorks portfolio.