Our work in the initial stages of this project is to demonstrate that the basic concept is feasible and that a free-flying helicopter of the dimensions envisioned here can be constructed. Our goal in the first six months is to focus on the potential barriers to the flight vehicle success, demonstrating how these will be overcome through working hardware, starting at somewhat larger scales than will eventually be achieved.
In November we assembled our team of students, faculty, and outside consultants. Starting in November we established weekly meetings of the entire team. The summaries that follow are summaries of work reported at these weekly meetings.
It was decided that, in parallel with the development of the 1mm micro-motor, we would design a larger rotor that could utilize a commercially-available 3mm motor.
The motor is a critical element that determines the design of the entire mesicopter. Once a motor design has been chosen and its performance is known, a rotor can be designed for maximum thrust with the motor. Based on these thrust estimates an airframe can be designed to hold the motor, the motor controller(s) and as much battery as the rotors can lift. In parallel the development of a high performance 1 mm micro-motor will be pursued which will in conjunction with the experience gathered from the larger mesicopter allow design and fabrication of a mesicopter with 1 cm diameter.
Faulhaber appears to be unable to deliver a sufficient number of their 1.9 mm motors within the next three months. The next smallest commercially available motor is the 3 mm smoovy motor (http://www.smoovy.com/products/syh39001.htm) Ten of these motors have been ordered for initial experiments, they should arrive here in December. After an extensive search there appears to be no suitable motor controller for these motors that would have a weight acceptable for the mesicopter application and we will consider building our own.
We are reviewing various methods of manufacturing the mesicopter rotor. Important interactions between manufacturing and preliminary design have been incorporated in the optimization process. We identified individuals with the following primary tasks:
Jim: Silicon processing, assistance with gel casting for ceramic parts, fabrication of bonded magnet parts for the micro motor.
Katsu: Assistance with polymer casting.
Fritz: General fabrication issues, interaction with SRI on battery fabrication.
Ilan, Mike: Rotor design. An initial rotor design is underway for the 3 mm motor. After that we will interactively modify the design to avoid problems on the fabrication side. Simulation, experiments, and optimization will determine the following:
- geometry: shape and acceptable thickness
- performance: thrust vs. rpm, power vs. rpm
- load: forces per unit area, important for material choice and thickness
- required geometric accuracy: critical parameters/dimensions
- interaction with adjacent rotors on the mesicopter.
Shelley: Rotor fabrication. A number of different methods has been established but not tried as of yet. Experiments will determine the following:
- rotor material: required stiffness/toughness, shape changes after support material removal due to internal stresses, machinability
- support material: compatibility with rotor material, removability, machinability
- shaping technique: machining, molding/casting, Si-process, limitations of these techniques and their impact on the rotor design.
Rudi: Mask design, motor controller design and tests, micro motor design optimization. Simulation and experiments will determine the following
- motor controller: 3 steps: separate circuit attached to mesicopter, integrated circuits soldered onto sputtered copper traces on airframe, integrated circuit as part of the Si airframe. Each step will bring significant weight reduction but will increase the cost and reduce flexibility.
- micro motor design: FEM simulation of the magnetic field for optimal performance while maintaining manufacturability. Simulation of both inside motor and outside motor.
Sam: Fabrication of a high performance 2 mm micro motor with jewel bearings.
This motor will be test bed for the performance simulations mentioned above. A modified version may become part of an intermediate mesicopter design
Scott: Air frame design and optimization
- structural design: minimize weight, adequate strength
- integration of motor, motor controller and battery
- automated assembly