Continuing from previously post (link), I’m going to continue the explain of development of this robot.
Hardware description
Introduction
The main parts of this robot are:
- Vehicle
- Smartphone
- Low level control board
- WSN node
Every part of this robot have been chosen according with the previous restrictions. The smartphone is the main part of the mobile robot, which communicates with the other elements through three different interfaces. The communication with ground station will be through Wi-Fi and UDP protocol. The communication with control board will be through Bluetooth v3.0. Finally the communication with WSN sensor will be through USB Host – RS232. Control board will receive velocity and rotation angle target from Bluetooth interface. In case of failure there is a security protocol to recover the mobile robot. This protocol allow control the robot through RF signal.
Vehicle
The vehicle is a revision of RC Rock Crawler. This is the structure where every components is mounted. The vehicle has two independent motors with a high precision velocity control (ESC) and shock absorber. llows a maximum rotation of 30 degrees on each side and a speed of 0.5 m/s. It measures 430 mm large, 258 mm width and 200 mm height.
We have chosen this model for its ability to walk on different terrains like we’re going to find in Doñana. All parts are balanced to adjust the center of gravity to the screw from which it will collect the helicopter. Lightweight carbon structure for attaching a two-dimensional graphic code is incorporated. This code allows the helicopter to identify, through a camera incorporated therein, the exact orientation and position of the gripping of the car.
Smartphone
The high-level control of the vehicle is done by a smartphone Samsung Galaxy SII, it has been chosen for solving communication and location constraints. We are not allowed to use the Wi-Fi standard 2.4 GHz because of potential interference in control of the helicopter, so we use its ability to connect to a network 5GHz frequency. For the restriction of location is not possible to find the position of the robot within the maximum error is being proposed with the GPS sensor. You will need to possess smartphone USB Host to connect to a mobile node communication. With this node we can use a network of sensors for precise localization. The main features that have chosen this smartphone are:
- Android development platform based on Java.
- Size and Weight: 125.3 x 66.1 x 8.49 mm and 117 g.
- Bluetooth 3.0.
- Wi-Fi two frequencies 5 to 2.4 GHz
- USB-Host
- A-GPS
- Gyroscopes and accelerometers
Low-level Control board
Board is composed of a series of elements which form the integrator proportional controller, these elements are:
- Bluetooth, BlueSMiRF WRL-10268 model for serial communication between the smartphone and the control board. Communication consist of a message composed by the speed and angle of rotation of the wheels and a security code for verification, some features are:
- Transmit current consumption 65mA, reception: 35mA.
- Inputs / outputs with 3.3V or 5V logic (also RS-232).
- Secure communication, 128-bit encryption.
- Size: 15mm x 43mm.
- PIC microprocessor programmed to receive two possible entries (Bluetooth and radio controlled). The microprocessor will prioritize radio controlled if both are received. The microprocessor send the control command to the robot servo returning to smartphone speed, steering angle and actual through bluetooth transmitter battery.
- A low voltage alarm for LIPO battery and a type of two cells (7.4V) battery
- Receiver Futaba FASST system R6106 HFC 6-channel 2.4 GHz and especially suitable for models with carbon fuselage. For Bluetooth signal loss, as a security measure, the receiver used to receive control commands from a radio control for recovery.
- Channels: 6.
- Voltage: 3.3 to 8.5 V.
- Dimensions: 22 x 39 x 12 mm.
- Weight: 7 g.
- Servo directional HSR-5980 (see Figure 2.5b) digital control rapid response is coreless type and uses steel gears, other features are:
- Par: 30 Kg / cm.
- Speed: 0,17s 60 degrees at 6 V, 0,14s / 60 degrees.
- Dimensions: 40 x 20 x 37 mm.
- Weight: 68 g.
Sensor node
A sensor node is a device in a wireless sensor network that is capable of performing some processing, gathering sensory information and communication with other nodes connected to the network. This project will define static nodes and mobile node. Static nodes are deployed in a grid in an area. The mobile node will be incorporated in the mobile robot. This will be used for receiving messages from the network to the location as explained in the next post. Description node used:
Nodes that are used are called a wireless Telos B. This node is a wireless module and very low power consumption for use in sensor networks, monitoring applications. Features of this model Telos Revision B:
- Interoperability with other units with the IEEE 802.15.4 standard.
- 8MHz Microcontroller MSP430 (10k RAM, 48K Flash).
- Integrated antenna Range: 50m indoors, 100m outdoors.
- Integrated sensors for humidity, temperature and luminosity.
- Ultra low power.
- Quick activation from hibernation.
- Programming and data collection via USB.
- Implementation of communication and meshed networks through support of TinyOS.
In the next chapter software description.
I love this small robot. One of the biggest strengths is the possibility to control your boss before breaking into the office.
It does look to have a lot of low level implementation work. Was it easy to connect android with the physical devices? Any advice for people willing to implement anything similar?
Thanks for your comments. There are two devices: The first, node WSN, was very difficult because Android in that moment haven’t a official driver to RS232. The second device, the connection between Low-Level control board and the smartphone was easy because the bluetooth protocol it’s simple to connect. My advice for anybody with interest in this field is be patient and work with the code.