To fulfil the requirements of the project, a Bluetooth low energy programmable platform has been designed that implements the following basic functionality:
- Have a method to receive energy in some form
- Harvest and store this energy
- Monitor the level of the stored energy
- Have a hibernation mode where its energy usage is reduced to a minimum
- Execute a task, where it consumes the stored energy
- Avoid obstacles which will prevent its task from being completed
- Maximise its ability to have energy delivered efficiently
- Be able to repeat its sleep-work-sleep cycle indefinitely
- Be able to communicate with other machines
- Be able to report its current status
- Allow remote control and commands to be received
- Provide the ability to update its internal systems while in the field
The platform is motor driven allowing it to move; it contains various on-board short range and long range communication facilities and has facilities to detect its surrounding objects.
The energy delivery is in the form of solar energy, needing a solar panel to harness this energy.
The energy storage is in the form of capacitors (super caps). The solar panel charges up the capacitors providing an energy store available for later use.
Highly efficient energy harvesting has been implemented which maximises the absorption of very low amounts of available energy, manage its storage and provide reliable delivery.
The bot monitors the level of energy stored within the capacitors; when the level passes an upper HIGH threshold value, the bot wakes up and perform a task. As the bot uses the energy the level in the capacitors drops, when the level drops below a LOW threshold, the bot ceases performing task execution and returns to a minimum energy consumption mode, allowing the energy store to be again recharged from the solar panel.
The ‘task’ is to use motors to propel itself along the ground. As the bot is reliant on solar energy, when it moves, it provides the ability to track the direction of the brightest light. This is achieved using two photodiodes positioned either side of the bot. The photodiodes react to the light and allow current to pass dependent on the level of light they receive, the magnitude of this input is used to adjust the bots direction of travel.
Two motors installed on each side of the bot are used to propel it across the ground; the motors speeds are manipulated to control direction of travel.
Ultrasonic radars are located on the front and rear of the bot providing ‘eyes’, these provide an ability to discover objects and distances of objects located around the bot, this data is then used to change the bots direction of travel. The radars provide a means to prevent the bot from becoming stuck against an object which could restrict its ability to move.
The bot uses both a LOW and HIGH threshold to monitor its energy storage levels; this provides a hysteresis which prevents the bot from entering an infinite cycle of their wake-up energy requirements immediately depleting their accumulated energy storage rendering them needing again to recharge.
Infrared transmission and reception, allowing talking and hearing, coupled with near-field-communications (NFC) has been implemented to facilitate short distance intercommunication between bots.
Bluetooth LE (Low Energy) communications  is used for long-distance control and monitoring.
Bluetooth LE is designed for very low power operation, and is optimized for data transfer solutions. To enable reliable operation in the 2.4 GHz frequency band, it leverages a robust Adaptive Frequency Hopping approach that transmits data over 40 channels. The Bluetooth LE radio provides developers a tremendous amount of flexibility, including multiple PHY options that support data rates from 125...Read more »