Relay Transport is to deliver cargo in a segmented way using one or more means of transportation, by which to greatly improve the efficiency. The organization of relay transport includes several parts: calculate the transport capacity of different facilities, arrange cargo handover date and place, unloading and loading, etc.
Based on that, can we use two or more Maqueen Plus cars to make a relay transport project? For example, the first Maqueen Plus delivers cargo to a transfer station, then the second Maqueen Plus transport the cargo to the endpoint.
Function
In this project we will be using GamePad to control Maqueen bulldozer and mechanic Beetle, and let them transfer cargo to the endpoint by relay, and stack up neatly.
Transport Rule: control the bulldozer to push the cargo to the intermediate transit point, and then use the mechanic beetle to deliver cargo to the endpoint and put them in order. The project is completed successfully only when the cargo is stacked up neatly.
Bill of Materials
Hardware Connection
1. Assembly: install the push kit onto Maqueen Plus according to the instruction below.
Accessory List
Installation Steps:
Install the lift-type beetle onto Maqueen Plus.
Note: the lift-type beetle is composed of Maqueen beetle and forklift, and you just have to find the related accessories in the mechanic kit.
Bill of Material:
Assembly Steps:
Install the lift-type part, as shown below:
Then install the gripper part:
Install the two parts onto Maqueen Plus:
2. Connection: connect the two servos of the lift-type beetle to S1 and S2: the servo for controlling lift goes to S1, beetle to S2. Please do not reverse them.
Knowledge Field
This project will be mainly making use of wireless communication to control the Maqueen bulldozer and lift-type mechanic beetle. Micro:bit itself supports wireless communication that can be directly used to transmit data between mainboards.
In wireless communication, a mainboard can be used as a transmitter or receiver. In this relay transport, the Gamepad will be the transmitter, and Maqueen bulldozer and beetle will be the receiver.
1. What is wireless communication?
Radio communication is a kind of communication that uses the electromagnetic signal to transmit information across space instead of wire, optical fiber and other media. At present, this technology is mainly used in radio and television, cell phones, remote control, wireless networking and satellite communication.
2. How does wireless communication work?
The commonly-seen wireless communication used in mobile phones, WiFi or even satellite propagates data by radio waves.
Information Encoding: radio waves, (a kind of electromagnetic wave similar to visible light) have amplitude, frequency and phase elements that can be modulated by the transmitter, by which to encode and transfer information. Basically, this is how radio wave transmits.
Transfer Low-frequency Signal: it is known that human sound can only propagate through a limited distance. If we want our voice to travel further, how can we make that happen?
A hypothesis like this was made by scientists: If we want to reach a destination, it is for sure that walking is not as fast as taking a car. So, if the transmission of low frequency (audio) can also be like taking a car, get on a car, arrive at the destination and get off, then the long-distance transmission of low-frequency (audio) can be completed. But, where do we find a car for low-frequency?
Travel by High-frequency: high-frequency electromagnetic waves can carry more information per unit time than low-frequency waves, and perform better in keeping the completeness of the information. Hence, we can “store” low-frequency signals onto these high-frequency waves and send them out.
Signal transmitting: different transmitters employ high-frequency of various frequencies, and they do not interfere with each other. This is the process of signal transmitting.
How can we let low-frequency “get off the car”?
Signal Receiving: after the radio wave is transferred to the receiving place, the receiver will receive the signal and recover it.
Modulate Carrier Frequency: the signal received by the receiving antenna in the same period of time not only includes the signal we need, but also many signals of other frequencies. The reason why these radio signals adopt different carrier wave frequencies(p
3. micro:bit Radio Communication
The principle of micro:bit radio communication is based on radio waves. There is an antenna on the back of micro:bit that allows data transmission between two micro:bit boards.
Project Development
The Gamepad will be used to control Maqueen bulldozer and beetle. And they will transfer the goods to the destination in a relaying way. There are 3 steps in this project.
First of all, complete the program of the transmitter-Gamepad, use keys A and B to switch radio setting group and send commands to receiving end; then completes the program of the receiving end of the bulldozer, and executes the forward, backward, left turn and right turn commands according to the received command; finally completes the program of the receiving end of the lift-type beetle, and executes the instructions of forward, backward, left turn, right turn, gripper up, down, open and close according to the received commands.
Task 1: Program for the GamePad
1. Program Design
Step 1 Get to know Gamepad
It is a micro:bit-based gamepad with a joystick, and can be used as a remote control handle when plugging a micro:bit in.
Step 2 Function
In the project, the joystick will be mainly used to control the movement of Maqueen bulldozer and lift-type mechanic beetle. The buttons on the Gamepad will be used for moving the gripper up and down, and closing and opening the gripper.
The detailed commands are shown below:
2. Sample Program
3. Effect Display
Press down button A to enter radio group 1 control mode, button B to enter radio group 2 control mode. Move the joystick up to send the forward command “F”; move it down to send backward command “B”; move the joystick left or right to send left/right turn command “L” or “R”. Press down button “E” to send command “Up”; button C to send “Down”; button D to send “ON”; button F to send “OFF”.
Task 2: Maqueen Bulldozer
1. Program Design
Step 1 Maqueen Bulldozer
The bulldozer blade on the front of the Maqueen Plus can be used to push objects to the designated place, and it is suitable for applications like football matches, venue cleaning and so on.
Step 2 Function Analysis
In this project, the commands sent from the gamepad will be used to control the movement of the bulldozer. The flowchart is shown below:
2. Sample Program
3. Effect Display
Press down button A to enter the radio group 1, also the bulldozer controlling mode. Move the joystick to control the Maqueen Bulldozer to move forward/backward and turn left/right.
Task 3: Lift-type Mechanic Beetle
1. Program Design
Step 1 Introducing lift-type Mechanic Beetle
The lift-type mechanic beetle is composed of Maqueen forklift and beetle. And it will be used to pick up items and transfer them. The maximum height the beetle’s gripper can reach is about 10cm.
Step 2 Function Analysis
We will be using the joystick to control the Mechanic beetle’s movement, and the buttons to control the gripper to move up/down or close/open. Buttons E and C for up and down, D and F for open and close respectively.
3. Sample Program
4. Effect Display
Simulate the scenario of relay transport, put the Maqueen bulldozer to the starting point, and the lift-type beetle to the intermediate transfer station. Press button A to enter bulldozer controlling mode. Move the joystick to control the bulldozer to push the object to the transfer station; Press down button B to enter beetle controlling mode: button D for opening the gripper, F for closing, E for moving up, C for moving down. During the transferring, we can use these buttons to make Maqueen Plus pick up items, and move the joystick to let it transfer the items to the endpoint, and operate the gripper to stack up items neatly.
Project Development
Now, Maqueen plus has been able to successfully transport goods to the destination through the mechanic accessories. Next, we'll upgrade the difficulty: get all the Maqueen Plus mechanic car assembled, put them at three transfer stations, then operate the gamepad to control these cars to deliver cargo to the endpoint in order, the team who finished the task with the least time wins.
Tip：
1. Write the corresponding function program for each Maqueen Plus car and Gamepad.
2. Four players control the Mechanic cars with gamepad handles. After the first person’s Maqueen Plus pushed the cargo to the first relay point, the second player starts to operate his mechanic car to push the cargo from the first relay point to the second relay point, and so on until the cargo is transported to the destination. The one who finished the task with the least time wins.
3. In the process of the competition, players should only operate their Maqueen Plus cars via GamePad.
4. Once the order is determined, it can not be changed during the competition.
Program.zip 
