17.1 Project Proposal

Introduction

Wall climbing robots have a wide range of real-world applications, from performing inspections and maintenance tasks to goods delivery on structures with smooth surfaces. Traditional methods for accessing vertical surfaces—such as scaffolding, ladders, or human-operated drones—often come with safety risks, high costs, or limited maneuverability. A wall climbing robot that uses electromagnets for adhesion offers a promising alternative for environments with magnetic surfaces like steel structures, ship hulls, bridges, or industrial machinery.

Problem Statement

Designing a wall climbing robot using electromagnets involves several complex challenges in motion, force distribution, and coordination. Unlike ground-based robots, which rely on friction and gravity for stability, a wall climbing robot must actively generate adhesion forces while maintaining controlled movement in an inverted orientation. To start with, this requires force balancing between the electromagnets and the robot’s weight. The robot's motion profile must account for coordinated detachment and reattachment of electromagnets, enabling continuous turning and climbing sequences. A simple joint-based system is insufficient because the robot must actively engage and disengage magnetic adhesion in a controlled manner, all while preventing unintended slippage or detachment.

Mechanism

We have determined that a four-bar mechanism can effectively generate the desired motion profile for our wall climbing robot. This design utilizes a single motor to control the position of each linkage, converting a circular input into the necessary movement. By leveraging the 180-degree portion of the linkage’s motion, we can produce the upward and downward movement required for climbing. Figure 1.1 below is a MotionGen mockup illustrating our four-bar linkage in action.

Open

Open

Scope of Work

1. Design a four-bar linkage system that converts circular input into efficient climbing motion while ensuring stability through kinematic and force analysis.

2. Coordinate diagonal leg pairs to establish an alternating climbing cycle, implementing precise timing and phase control for synchronized movement.

3. Integrate a scissor-like mechanism between diagonal leg pairs to enable controlled turning independent of climbing motion.

4. Construct low-fidelity prototypes using laser-cut and 3D-printed components to test packaging layout.

5. Incorporate joystick controller to achieve climbing and turning capabilities.

6. Refine linkage dimensions, pulley system, and actuation while optimizing motor calibration and electromagnet control for efficient adhesion-release cycles.

Preliminary Design

Our design features a single motor driving four cranks (see Mechanism above) via a pulley system, with each four-bar linkage representing a leg in the robot's walking mechanism. The legs operate in diagonal pairs, meaning the bottom-left leg moves in sync with the top-right leg, and the bottom-right leg moves in sync with the top-left. Ideally, each leg follows a semi-circular path, where the 180-degree portion of this motion provides the necessary push to propel the robot upward. While one diagonal pair of legs moves, the other remains fixed to the surface using electromagnets for stability.

To enable turning and directional control, we incorporate a scissor linkage mechanism actuated by a separate motor. This mechanism allows for pure rotational movement, enabling the robot to adjust its walking direction. The turning process follows these steps:

1. One diagonal leg pair remains grounded via electromagnets while the other rotates to the desired angle.

2. The previously grounded pair then adjusts to align with the new direction.

3. Once reoriented, the walking mechanism resumes motion in the newly adjusted direction.

This coordinated interplay between the walking and turning mechanisms ensures controlled movement and maneuverability on vertical surfaces. See preliminary design in Figure 1.2 below.

Open