Linear Lift Mechanism

Learn to build and control linear lift mechanisms. Linear lifts use a straight-line motion to raise and lower loads, making them ideal for simple lifting applications.

Table of Contents

  1. Learning Objectives
  2. Mechanism Overview
    1. How Linear Lifts Work
    2. Applications in Robotics
  3. Build Instructions
    1. Interactive Assembly Guide
    2. Key Components
  4. Programming Control
    1. Basic Motor Control
    2. Position Feedback
  5. Mechanical Advantage
    1. Calculating Advantage
  6. Design Challenges
    1. Exercise 1: Load Testing
    2. Exercise 2: Precision Control
  7. Troubleshooting
    1. Common Issues
  8. Reference Resources
    1. Construction Video
    2. Next Steps

Learning Objectives

By the end of this lesson, you will be able to:

  • Understand the principles of linear motion systems
  • Build a functional linear lift mechanism
  • Calculate mechanical advantage in linear systems
  • Program motor control for precise positioning

Mechanism Overview

How Linear Lifts Work

Linear lifts convert rotational motion (from motors) into straight-line motion using:

  • Lead screws: Threaded rods that convert rotation to linear motion
  • Rack and pinion: Gear systems that move loads in straight lines
  • Belt and pulley: Flexible systems for smooth vertical movement
  • Hydraulic/pneumatic: Fluid-powered linear actuators

Applications in Robotics

  • Elevator systems: Raising robots to different levels
  • Lifting mechanisms: Picking up and placing objects
  • Camera mounts: Adjusting sensor height
  • Tool positioning: Precise linear movement of end effectors

Build Instructions

Interactive Assembly Guide

Key Components

  1. Base structure: Provides stable foundation
  2. Linear guide: Ensures straight motion without binding
  3. Drive mechanism: Motor and transmission system
  4. Load platform: Carries the objects being lifted
  5. Limit switches: Detect top and bottom positions

Programming Control

Basic Motor Control

// Pseudocode for linear lift control
void moveUp(int distance) {
    motor.start(UP_DIRECTION);
    delay(calculateTime(distance));
    motor.stop();
}

void moveDown(int distance) {
    motor.start(DOWN_DIRECTION);
    delay(calculateTime(distance));
    motor.stop();
}

Position Feedback

For precise control, add sensors to track position:

  • Encoders: Count motor rotations
  • Potentiometers: Measure linear position
  • Limit switches: Detect end positions

Mechanical Advantage

Calculating Advantage

Linear lifts can multiply force at the cost of speed:

Mechanical Advantage = Input Distance / Output Distance

For a lead screw with 4 threads per inch:

  • 1 motor revolution = 1/4 inch of lift
  • MA = 4:1 (4x force multiplication)

Design Challenges

Exercise 1: Load Testing

Build your linear lift and test with different weights:

  1. Start with light objects (100g)
  2. Gradually increase load
  3. Find the maximum lifting capacity
  4. Record the relationship between load and speed

Exercise 2: Precision Control

Program precise positioning:

  1. Move to exact heights (2”, 4”, 6”)
  2. Hold position for 5 seconds
  3. Return to starting position
  4. Measure accuracy (within ±0.1”)

Troubleshooting

Common Issues

Problem Possible Cause Solution
Jerky movement Binding in guide Check alignment, lubricate
Motor stalls Load too heavy Reduce weight or add gearing
Inconsistent position Backlash in drive Adjust tension, add preload
Slow movement Insufficient power Check battery, motor voltage

Reference Resources

Construction Video

Linear Lift Construction Guide

Note: This video uses slightly different robot parts than we have in class, so adapt the design to match our available components.

Next Steps