CHAPTER 5: SYSTEM DESIGN AND CONSTRUCTION
5.3. Design and construction of electrical and control systems
5.3.2 Select equipment for the system
5.3.2.1 Board Arduino MEGA 2560 and MEGA pro 2560
➢ Arduino Mega 2560:
• Size: Larger, suitable for projects that need a lot of space for components and connections.
• Connection: Full range of connection pins, including power pins, digital I/O pins, analog pins, serial communication pins, PWM pins, SPI pins, I2C pins.
• Application: Suitable for large, complex projects that require a lot of resources and scalability.
Figure 5.23: Structure of the Arduino mega 2560
➢ Arduino Mega 2560 Pro (Embed):
• Size: More compact, suitable for projects requiring mobility and space saving.
• Connection: Maintain the important connection pins, but some rarely used pins can be removed to reduce size.
• Application: Ideal for compact, embedded projects that require high performance but do not need too many connection pins.
Figure 5.24: Pinout diagram of Mega 2560 Pro
Table 5.1 Arduino Mega 2560 and Mega 2560 Pro parameters
Features Parameters
Microcontroller Atmega2560
Operating frequency 16 MHz
Operating voltage 5V
Number of I/O pins 54 pins (including 15 PWM pins)
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Analog input channels 16 channels
UART interfaces 4
SPI interface 1 (pins 50 - 53)
I2C interface 1
Interrupt ports 6 ports
Flash memory 256 KB
SRAM 8 KB
EEPROM 3 KB
5.3.2.2 Dynamic expansion motor for grass cutting mechanism
The engine functions as the main engine to rotate the lawn mowing mechanism.
The engine will have a rotating capacity of 1400rpm/V.
Figure 5.25: Motor-sunnysky X2212-8
Figure 5.26: ESC 20A Here the motor voltage will be supplied by the 20A ES
5.3.2.3 Step motor with speed reduction gear boxes SK4248
2 Step 42 motors equipped with gear reduction boxes are used to facilitate the movement of the grass-cutting mechanism. One motor controls the vertical adjustment of the cutting mechanism to regulate the cutting height, while the other motor manages the extension and retraction of the grass-cutting unit during operation.
Figure 5.27: Step 42 motor with speed reduction
DEPARTMENT OF AUTOMATIC CONTROL 74 Figure 5.28: Mechanical drawing of the motor
Table 5.2 Step Motor Parameters
Features Parameters
Voltage 12V
Current no Load 1.5 A
Motor Step 1.8o/step
Torsional moment 0.55 Nm
Output Shaft 8 mm
Motor Ratio 1:13.7
5.3.2.4 Planetary DC motor
The Planet 30W 600RPM motor with a 12PPR encoder and 8mm shaft is a versatile and efficient motor designed for precise control applications. With a power rating of 30 watts, it operates at a steady speed of 600 revolutions per minute, making it ideal for tasks requiring consistent and reliable performance. The integrated encoder provides 12 pulses per revolution, offering accurate feedback on motor position and speed, which is crucial for applications in robotics, automation, and CNC machinery.
Figure 5.29: Motor Planet 30W 600 rpm
Figure 5.30: Mechanical drawing of the motor
Table 5.3 DC Planet Motor Parameters Features Specifications
Voltage 12-24V
Output Shaft 8mm
Current (no load) < 300 mA
Current (full load) 3600 mA
Motor Ratio 1:29.2
Encoder 12 pulses, 2 channel A,B
Power 30 W
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Torsional moment 0.363 Nm
Mass 450 g
5.3.2.5 Stepper Motor Driver TB6600
Two TB6600 step drivers are employed to control the pulse supply to the two stepper motors. Both drivers are configured with a micro step setting of 8 (OFF-ON-OFF) to suit the pulse supply requirements for both motors.
Figure 5.31: Stepper Driver TB6600
Figure 5.32: Stepper Driver TB6600 Wiring diagram
Table 5.4 Stepper Driver TB6600 Parameters Features Specifications
Input Voltage 9V – 42V
Input Current 0 – 5 A
Output Current 0.5 – 4 A
Power (MAX) 160 W
Micro Step 1, 2/A, 2/B, 4, 8, 16, 32
Dimension 96*56*33 mm
Weight 200g
Temperature -10～45℃
5.3.2.6 HI216 H-Bridge circuit
The HI216 H-Bridge circuit is an essential component used to control the direction and speed of DC motors. It allows for full bidirectional control by enabling the motor to run forward, backward, or stop. The HI216 is designed to handle high current and voltage requirements, making it suitable for various applications, including robotics, automotive systems, and industrial automation. With its efficient design, the HI216 H-Bridge ensures
DEPARTMENT OF AUTOMATIC CONTROL 78 minimal power loss and provides robust protection against overheating and short circuits, ensuring reliable performance in demanding environments.
Figure 5.33: HI216 H-Bridge circuit
Figure 5.34: Wiring diagram of HI216 H-Bridge
Table 5.5 HI216 H-Bridge Circuit Parameters Features Specifications
Output Voltage 12V – 48V
Control Logic Voltage 3 – 5 V
Continuous Current Output 2 A
Dimension 52*64*22 mm
Weight 50g
5.3.2.7 LM2596 Step Down Buck Converter
The LM2596 step down buck converter is used to step down the voltage from the vehicle's power supply to 5V, providing power for the MCUs, encoders, and other components.
Figure 5.35: LM2596 DC-DC Step Down Buck Converter
Table 5.6 DC-DC Step Down Buck Parameters Features Specifications
Input Voltage 3V – 30V
Output Voltage 1.5V – 30V
Maximum Response Current 3 A
Power 15W
Dimension 45x20x14mm
5.3.2.8 SX1278 433MHz RF LoRa AS32 UART Transceiver Module
Our team uses the SX1278 433MHZ RF LoRa AS32 transceiver module for transmitting signals to the remote controller due to its compact size, enabling wireless connectivity that is easy to use, stable, cost-effective, and suitable for long-distance transmission with minimal obstruction from obstacles. It can achieve a maximum range of up to 3000 meters in ideal conditions without obstacles.
DEPARTMENT OF AUTOMATIC CONTROL 80 Figure 5.36: LoRa AS32 UART Transceiver Module
Figure 5.37: LoRa AS32 UART Transceiver Module Wiring diagram
Table 5.7 LoRa AS32 UART Transceiver Module Parameters Features Specifications
Input Voltage 2.3V – 5.5V
Output Voltage 5V – 35V
UART Communication Data bits 8, Stop bits 1
Frequency 410 – 441Mhz
Maximum Transmission Distance
3000 m
Transmission Rate 0.3 – 19.2 Kbps (Default: 2.4 Kbps)
Power 20dbm (100mW)
Weight 20g
5.3.2.9 Anten WiFi 4G RF LoRa
Figure 5.38: Anten WiFi 4G RF Lora
Table 5.8 Anten WiFi 4G RF Lora Parameters Features Specifications
Gain 8 dBi
Output Voltage 5V – 35V
UART Communication Data bits 8, Stop bits 1
Frequency Range 700 – 2700 Mhz / 433Mhz / 315Mhz
Noise ratio <1.5 dB
Transmission Rate 0.3 – 19.2 Kbps (Default: 2.4 Kbps)
Power 50W
Length 230mm
Working Temperature -40～85℃
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Weight 28g
5.3.2.10 Camera integrated with VTX module
The Camera integrated with VTX is used to transmit the real-time vision from the Lawn Mowing Robot so that the user can control the robot manually from a long distance.
Figure 5.39: Camera integrated with VTX module and RTX Module
5.3.2.11 Battery Ovonic 2600mAH 4S 50C
A well-functioning robot requires a stable power source and high discharge current.
Therefore, the group using 4S 14.8V Lipo battery to power the speed controller circuit is a reasonable choice with the advantages of compact size, light weight, good performance and safety. Besides, use this battery source through the voltage reduction circuit to power the Servo, DC motor control circuit, and microcontroller.
Figure 5.40: Battery Ovonic 2600mAH 4S 50C Table 5.9 Lipo Battery Parameters
Features Specifications
Capacity 2600mAh
Discharge 75C
Cell 4 S
Voltage for each cell 14.8V
Weight 252g
Dimension 106*35*33mm
5.3.2.12 Compass Sensor HMC5883L
To maintain balance during operation, sensors play a crucial role in controlling the lawn mowing robot. To effectively control the robot, we need to collect information such as angular acceleration, angular velocity, device orientation angles, ground clearance, and magnetic field data. Key sensors include feedback accelerometers and inertial
DEPARTMENT OF AUTOMATIC CONTROL 84 accelerometers, which provide essential signals for the robot to maintain stability and ensure efficient control during lawn mowing operations.
Figure 5.41: HMC5883L Compass Sensor
The lawn mowing robot uses the HMC5883L sensor to help the lawn mowing robot measure the Yaw angle. The HMC5883L sensor is a three-axis magnetometer, commonly known as a digital compass. Manufactured by Honeywell, this device measures the intensity and direction of the magnetic field in three dimensions, accurately determining the Earth's geomagnetic orientation. This makes the HMC5883L a critical component in positioning and navigation systems, especially in applications like drones, autonomous robots, and GPS devices. The sensor communicates via I2C or SPI interfaces with microcontrollers, facilitating easy integration into various electronic systems. Additionally, the HMC5883L is equipped with noise filters and internal amplifiers to enhance measurement accuracy and stability of magnetic field readings. With high resolution and low power consumption, the HMC5883L is an ideal choice for projects requiring precise magnetic field measurement and positioning.
Table 5.10 HMC5883L Compass Sensor Parameters Characteristics Parameters
Power supply 3-5V
Measurement threshold 1.3 – 8 gauss
Accuracy 2%when full-scale
Resolution 16 bit
Communication method I2C
Dimensions 4*4*0.9 mm
Weight 0.06 g
5.3.2.13 GPS iFlight BLITZ M10 QMC5883L
Factors to consider when choosing the right GPS chip for the application:
• Accuracy: This is the most important factor when choosing a GPS chip. High accuracy will help your positioning and navigation system work more effectively.
For applications that require precise location such as lawn mowing robots, choosing a highly accurate GPS chip is necessary to ensure the robot moves as desired.
• Update rate: The GPS chip's update rate is the number of times location data is updated per second. High update rates help devices respond more quickly to changes in position, which is especially important in applications that move quickly or require timely responses such as drones, autonomous vehicles, and cutting robots grass.
• Sensitivity: The sensitivity of the GPS chip determines its ability to capture signals in different environmental conditions. The highly sensitive GPS chip will work well even in areas with weak signals such as dense forests, urban areas with many tall buildings, or under trees.
• Time to first acquisition (TTFF): TTFF is the time it takes the GPS chip to determine position from start-up. Fast first signal acquisition time helps devices start up and be ready for operation in less time, improving overall system performance.
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• Ability to integrate other sensors: Some GPS chips integrate additional sensors such as magnetic fields, accelerometers, or gyroscopes to improve positioning and navigation capabilities. This integration capability is useful in applications that require accurate and comprehensive positioning information.
• Power consumption: For battery-powered applications such as drones or autonomous robots, choosing a GPS chip with low power consumption is important to extend device operating time.
• Size and weight: The size and weight of the GPS chip needs to match the overall design of the system. For compact applications such as wearables or drones, choosing a GPS chip that is small in size and light in weight will help optimize the design.
• Anti-interference ability: In some environments, GPS signals may be interfered with by other signals. GPS chip with good anti-interference ability will ensure the stability and accuracy of location data.
• Cost: Finally, cost is a factor that cannot be ignored. It is necessary to consider the price, features, and accuracy of the GPS chip to choose a product that suits the budget and requirements of the project.
By carefully considering these factors, you will be able to select the most suitable GPS chip for your application, ensuring system performance and reliability.
Specific values of factors to consider when choosing GPS chips for lawn mowing robot applications:
- Accuracy:
Specific value: Accuracy from 1.5m CEP (Circular Error Probable) or less.
Reason: Ensure the lawn mowing robot can move correctly along the desired cutting path, avoiding missing or repeating cutting areas.
Update speed:
Specific value: Minimum 5 Hz, ideally 10 Hz.
Reason: Ensure the robot can respond promptly to changes in position, helping to move smoothly and accurately.
Sensitivity:
Specific value: -165 dBm or lower.
Reason: Helps GPS chips work well even in difficult environmental conditions such as areas with many trees or houses.
Time to first acquisition (TTFF):
Specific values: Cold start < 35s, hot start < 1s.
Reason: Ensure the robot can start up and locate quickly, ready to operate in a short time.
Other sensor integration capabilities:
Specific value: Integrated magnetic field sensor (magnetometer) such as QMC5883L.
Reason: Magnetic field sensors help improve positioning accuracy by providing information about the direction of movement.
Energy consumption:
Specific value: Less than 100 mW.
Reason: Ensuring energy savings, extending robot operating time when using batteries.
Size and weight:
Specific value: Dimensions less than 30mm x 30mm x 10mm, weight less than 20g.
Reason: Makes it easier to integrate into the robot's design without increasing the overall size or weight too much.
Anti-interference ability:
DEPARTMENT OF AUTOMATIC CONTROL 88 Specific value: Integrating advanced anti-interference technologies.
Reason: Ensures the stability and accuracy of location data in environments with many interfering signals.
Expense:
Specific value: From 20 to 50 USD.
Reason: Balance price and features, ensuring the product fits the project's budget while still fully meeting performance and accuracy requirements.
➢ From the above specific factors we have selected iFlight BLITZ M10 QMC5883L chip for the lawn mowing robot project:
High accuracy: iFlight BLITZ M10 is a modern GPS chip with high accuracy, ensuring precise positioning of the lawn mowing robot. This is important in ensuring that the robot moves correctly along the desired cutting path and does not miss any areas.
Fast update speed: The M10 chip has a fast data update speed, helping the robot respond promptly to changes in position. This is necessary to ensure that the robot can move smoothly and accurately.
Integrated magnetic field sensor QMC5883L: 3-axis magnetic field sensor QMC5883L provides information about the direction of movement, helping the robot maintain accurate direction and improving the stability of the positioning system.
Basis for choosing iFlight BLITZ M10 QMC5883L chip:
High sensitivity: M10 GPS chip is capable of capturing good signals even in difficult environmental conditions, such as areas with many trees or high-rise buildings.
Durability and reliability: iFlight is a reputable brand in the field of manufacturing remote control aircraft and GPS modules, ensuring products are highly durable and operate stably for a long time.
Easy integration: This GPS module easily integrates with popular microcontrollers and embedded systems, making programming and use simpler.
Figure 5.42: GPS iFlight BLITZ M10 QMC5883L Advantages when applied to lawn mowing robots:
Accurate positioning: With the high accuracy of the M10 GPS chip, the lawn mowing robot can accurately locate each location on the garden, ensuring the entire area is mowed regularly.
Improved performance: The chip's fast update speed helps the robot respond quickly to changes in position, improving working efficiency and reducing mowing time.
Precise guidance: QMC5883L magnetic field sensor helps the robot maintain precise direction, avoiding deviation or repeating cut areas.
Defect:
High cost: Some modern GPS modules such as iFlight BLITZ M10 are quite expensive, which can increase the overall cost of the project.
Programming requirements: To take full advantage of the chip's features, users need to have good programming skills and understanding of the navigation system.
DEPARTMENT OF AUTOMATIC CONTROL 90 Table 5.11 GPS iFlight BLITZ M10 QMC5883L Parameters
Features Specifications
Input Voltage 3.3V – 5.5V
Baud Rate 4800bps-921600bps
Maximum Speed 500 m/s
Speed Accuracy 0.05 m/s
Update Rate 10 Hz
Maximum Altitude 80000 m
Sensitivity -167dBm
Communication Interface UART / I2C
GNSS System GPS+SBAS+Galileo+QZSS+Glonass
Dimensions 25x25x6 mm
Weight 16 g
5.3.2.14 Alarm buzzer
An alarm buzzer is used to emit a warning sound when the camera detects a person in working area.
Figure 5.43: Alarm buzzer
DEPARTMENT OF AUTOMATIC CONTROL 92 Table 5.12 Alarm buzzer Parameters
Features Specifications
Input Voltage 9V – 12V
Working current 100mA – 170mA
Sound intensity 110dB
Working temperature -10～50℃
5.3.2.15 1-Channel Relay Module 5V with Optocoupler H/L Level Trigger A 1-Relay Module with opto-isolation is used, featuring an optocoupler and transistor isolation to ensure safe operation with the main board. The 1-Relay Module with 5V opto- isolation is used to switch the power supply for the alarm buzzer. When a high-level signal is received from the MCU, the NO (Normally Open) pin will connect to the COM (Common) pin, activating the relay to power the buzzer.
Figure 5.44: 1-Channel Relay Module 5V
Figure 5.45: 1-Channel Relay Module Wiring diagram Table 5.13 1-Channel Relay Parameters
Features Specifications
Supply Voltage (DC) 5V
Consumed current 80mA
Maximum switching voltage AC 250V ~ 10A or DC 30V ~ 10A
Dimension 50*26*19mm
Weight 17g
5.3.2.16 FLYSKY FS-i6X 2.4GHz AFHDS Transmitter
To manually control the robot, a handle is required. Therefore, the FLYSKY FS-i6X 2.4GHz AFHDS Transmitter will be used to transmit manual control signals to the robot.
DEPARTMENT OF AUTOMATIC CONTROL 94 Figure 5.46: FLYSKY FS-i6X 2.4GHz AFHDS Transmitter
Table 5.14 FLYSKY FS-i6X 2.4GHz AFHDS Transmitter Parameters Features Specifications
Supply Voltage (DC) 6 V
RF Range 2.408-2.475GHz
RF Power < 20dBm
Channel 10
Bandwidth 500KHz
Maximum switching voltage AC 250V ~ 10A or DC 30V ~ 10A
Dimension 174*89*190mm
Weight 392g
5.3.2.17 Flysky FS-iA10B10CH Receiver
The Flysky FS-iA10B 10CH Receiver is used to receive signals transmitted from the controller, then sends these signals to the MCU to control the robot according to the controller's signals.
Figure 5.47: Flysky FS-iA10B10CH Receiver
Table 5.15 FLYSKY FS-i6X 2.4GHz AFHDS Transmitter Parameters Features Specifications
Supply Voltage (DC) 4- 6.5 V
Frequency Range 2.4-2 .48 GHz
Receiver sensitivity -105dBm
Channel 10
Bandwidth 500KHz
Maximum switching voltage AC 250V ~ 10A or DC 30V ~ 10A
Dimensions 47*33*14mm
Weight 19.3g