Case 1: Weightlifting Robot

Case Introduction

Design a weightlifting robot that can automatically perform tasks without programming. The robot uses a crank-connecting rod mechanism to convert the circular motion of the motor into linear reciprocating motion to achieve weightlifting movements.

Teaching Preparation

Name	Graphic
Nezha Pro Sport Kit

Teaching Objectives

Understand basic mechanical principles such as levers, pulleys, and crank-connecting rod mechanisms.

Develop hands-on and problem-solving skills.

Inspire interest in engineering and robotics.

Course Introduction

Welcome children to join our STEAM journey! Today we are going to transform into little engineers and make a magical weightlifting robot together. No complicated programming is required. We only need a simple crank-connecting rod to make the robot move and lift heavy objects. Isn't it cool? Let's explore the mysteries of mechanics together, use our hands and brains, and start the fun of creation!

Learning Exploration

Explore how the crank-connecting rod mechanism works.

Building Steps

Case Demonstration

Press the button on Nezha Pro to let the weightlifting robot start lifting weights.

Summary and sharing

Expand your knowledge

Working principle of crank-connecting rod mechanism The crank-connecting rod mechanism is the basic mechanism in the internal combustion engine that converts the reciprocating linear motion of the piston into the rotational motion of the crankshaft (or vice versa). It is used in many mechanical systems. Let's explore its working principle:

Basic components:

Crankshaft: A rotating shaft, usually with one, two or more cranks. Connecting rod: A rod connecting the piston and the crankshaft. Piston: A component that reciprocates in the cylinder. Working principle:

When the piston is pushed in the cylinder, it transmits force to the crank on the crankshaft through the connecting rod. The connection point between the crank and the connecting rod is called the piston pin, which allows the connecting rod to rotate around it. The rotation of the crank causes the connecting rod and the piston to move in a coordinated manner, thereby converting linear motion into rotational motion. Motion conversion:

Linear to rotation: When the piston moves downward, it pushes the connecting rod, and the other end of the connecting rod pushes the crank, causing the crankshaft to rotate. Rotation to Linear: If the crankshaft is driven to rotate by an external force (such as a motor), the rotation of the crank will pull the connecting rod, which in turn pushes the piston to move linearly in the cylinder. Transmission of Force:

The design of the crank-connecting rod mechanism allows the force of the piston to be effectively transmitted to the crankshaft, thereby driving other mechanical parts, such as wheels or generators. Important Parameters:

Stroke: The distance from the top dead center to the bottom dead center of the piston. Compression Ratio: The ratio of the total volume of the cylinder to the volume of the combustion chamber, which affects the efficiency and power output of the engine. Optimization and Adjustment:

By adjusting the length of the crank and the design of the connecting rod, the performance of the engine can be optimized, such as increasing power output or improving fuel efficiency. Practical Application:

In addition to internal combustion engines, crank-connecting rod mechanisms are also used in other occasions that require conversion between linear and rotary motion, such as reciprocating pumps, compressors, etc.

Differences and application scenarios between circular motion and linear motion

Circular motion and linear motion are two basic forms of motion that differ significantly in their physical properties and application scenarios. Here is a discussion of the two types of motion:

Circular Motion Definition:

Circular motion is the motion of an object along a circular or curved path.

Features:

Path: The trajectory of an object's motion is a continuous curve.

Velocity change: The magnitude of the velocity may remain constant, but the direction keeps changing, so there is a centripetal acceleration.

Requires an external force: In order to maintain circular motion, an object needs a continuous centripetal force.

Application scenarios:

Watches and clocks: The rotation of the hour, minute, and second hands.

Revolving door: The rotation of the door allows people to enter and exit.

Merry-go-round: A rotating facility in an amusement park.

Wheels: The wheels of a vehicle enable the vehicle to move along a straight or curved path.

Planetary motion: In astronomy, the orbital motion of a planet around the sun.

Linear Motion Definition:

Linear motion is the motion of an object along a straight path. Features:

Path: The trajectory of an object's motion is a straight line.

Speed change: The magnitude and direction of the speed can change, but no centripetal force is required.

Simple and direct: Linear motion does not require a complex balance of forces and is easy to control and predict.

Application scenarios:

Elevator: An elevator that moves vertically or horizontally.

Slide: A slide in an amusement park where children slide down in a straight line.

Conveyor belt: A conveyor belt used to transport items in a factory.

Trains and subways: Transportation that runs in a straight line along a track.

Retractable door: A door that can be retracted in a straight line, used to control the entry and exit of vehicles and pedestrians.

Difference: Different paths: The path of circular motion is a curve, while the path of linear motion is a straight line.

Direction of velocity: In circular motion, the direction of velocity always points to the tangent direction of the circle, while in linear motion, the direction of velocity remains unchanged or changes along a straight line.

Acceleration: There is centripetal acceleration in circular motion, while there is only tangential acceleration in linear motion (if the velocity changes). Force requirement: Circular motion requires centripetal force to maintain, while linear motion does not require such force (unless there is acceleration). Understanding the difference and application scenarios of these two types of motion can help us design and analyze various mechanical systems and daily equipment, so as to make more reasonable decisions in engineering and scientific research.

Related Knowledge of Weightlifting

Weightlifting is a sport with a long history. Here is some related knowledge about weightlifting:

Project Introduction

Weightlifting is a strength sport. Athletes need to lift the barbell overhead with both hands through specific movements, reach a specified height and maintain stability, demonstrating maximum strength and explosive power.

Modern weightlifting competitions include two events: the snatch and the clean and jerk. In the snatch, athletes are required to lift the barbell directly overhead from the lifting platform in a continuous motion, keep their bodies upright. After the barbell stays stable overhead, the referee signals success and the movement is completed. The clean and jerk consists of two steps. First, lift the barbell to the chest and support it between the collarbone and both shoulders, and then lift the barbell overhead.

Competition Rules

Weightlifting competitions are divided into different weight categories for both men and women. In the competition, athletes have three attempts. The highest successful weights in the snatch and the clean and jerk are added together as the total score to determine the ranking of the competition. If the total scores are the same, the athlete with the lighter body weight wins.

During the competition, athletes' movements must comply with the rules. For example, the barbell must rise and fall vertically, and the body posture must be correct. Otherwise, it will be judged as a foul and the attempt will fail.

Training Methods

Weightlifting training requires the comprehensive development of athletes' physical qualities such as strength, speed, coordination, and flexibility. Common training methods include barbell training, such as squats, bench presses, deadlifts, etc. These movements can effectively improve the muscle strength of the legs, hips, chest, and back.

In addition, there are some training specifically for weightlifting techniques, such as decomposition exercises of the snatch and the clean and jerk, as well as various auxiliary trainings, such as balance training and explosive power training, to help athletes better master weightlifting techniques and improve their athletic performance.

Important Competitions

The weightlifting competition in the Olympic Games is the highest-level international event in the weightlifting project. It is held every four years and attracts the best weightlifters from all over the world. In addition, the World Weightlifting Championships is also an important international event, held once a year, providing a platform for athletes from various countries to showcase their strength and communicate. In regional competitions, such as the Asian Games, Pan American Games, etc., weightlifting is also one of the important competition events.