Readings and Videos
Festo Robot Arm – Airic’s Arm Video
Kingsley Dissertation (CWRU) 2005
Chou 1997 [Study of human forearm posture maintenance with a physiologically based robotic arm and spinal level neural controller]
I assume that Braided Pneumatic Actuators is the name of the actuator type you were talking about. Looks promising. The same guy that made the cricket is using this new type of actuator for a robot arm. By the way, the Cricket Robot V3 we saw was using double acting pneumatic cylinders.
Pneumatic Cylinders
Double Acting Pneumatic Cylinders are used to push and pull air. This means that we can control a component in both directions. A Single-Acting Pneumatic Cylinder is used when you want to push or pull air, but in the reverse direction is done by just blowing the load. The cylinders come in various diameters which help to produce a specified amount of force. Such as a 2.5mm cylinder is used to lift microchip components while 400mm diameter cylinder is used to lift a car. The force is related to the air pressure flowing into the cylinder times the cross sectional area of the cylinder.
In the application of the arm muscle is considered a rodless, single-acting actuator. The controller that connects to the arm would be in charge of how the air is delivered and received from the muscle. The company Festo provides these actuator types that can apparently be cut and fitted on site.
This link is supposed to be the pneumatic muscle provided by Festo. This is the same company that was used by the robot arm I found on the web and used by the updated version of the cricket robot.
Air Compressors
We need a specified amount of air pressure to designate the ’strength’ of the muscles of the arm. This means we need an air compressor with more pressure than is required that has some type of regulator. There are two sources we could look for air pressure. There are air lines in the lab that could be used to ‘power’ our muscle. We need to find out what the expected output of the line is by the building manager and a regulator would need to be installed on the arm to make it possible to select the amount of pressure desired. The other option is to go with a high output, quiet compressor. Such as this Huskey offered at the HomeDepot which has its own regulator and sufficient pressure.
Air Control Valves
There are multiple types of control valves and methods of control. The schema for the valves is V/P NO/NC. Where V is the number of valves offered where two is the minimum for air input and device output, three will add an exhaust or two device outputs. P is the number of positions where two is the minimum of push and release, three will add a third state which is variable depending on the type of valve purchased but is typically to hold the current air pressure. NO means normally open and NC means normally closed in the unactuated state.
The means of controlling a valve is by an actuator. This is an internal spring type which a spring will force the valve to its natural state when the external valve is open. An air pilot actuator can be used where air can be used to enable the air actuator. A solenoid actuator, also called direct acting actuator, is an actuator that is controlled electronically. These tend to be faster and is more along the lines of what we need for our project. These are meant for low pressure applications and tend to have some problems with getting gunked up if the air supply has a lot of moisture and dirt in it. In high pressure applications a direct acting actuator may not be enough and a Solenoid Pilot Valve Actuator may be needed. The problem with this type is that it has a minimum flow which would be determined by the manufacturer but is typically around 20 to 25PSI.
Manifolds
One method of distributing are from one compressor to multiple outputs is the use of an Air Manifold. These have an inlet and one of many outputs that can connect to the external systems. A compressor system would need to provide sufficient air pressure to the system to not be taxed by the multiple devices connected to the outputs. Regulators used at the outputs can be used to regulate the appropriate air pressure to each of the subsystems.
Regulators
Regulators are as their name suggest. They regulate the air pressure that passes from the input to the output. Some regulators, filtered regulators, contain a filtration system within the regulator to help eliminate problems of dirty air passing to the more delicate air control valves.
Pneumatic Retailers
Micro Controllers
The PICs are cheap, like 5 bucks, for the nicest one on the market. But then you are expected to purchase a demo board or some type of board for flashing the PIC. Can you not just use the PIC stand-alone by wiring it up to a serial port or is there some crazy configuration for programming the chips?
I found that there are $25 “plug-in modules”. This suggests that you have to plug it into another board to utilize it. They say that you have to plug it into the Explorer 16 Demo board. Explorer 16 demo board is $130.
There is an option to receive samples. I will read a little more what this entails but I believe we need to contact them what we plan to do and give them a little proposal. Then we need to show them that we are linking people from our project page to their page or mentioning them several times.
The plug-in module literally plugs into a location in the center of the board. The demo board has anything you can want. LCD display, telephony cables, usb, serial… something else… a small prototyping area.
I vote we just go for the best they have to offer. It is the same price and it looks like if the need arises we can control anything else we apply to the robot arm as a controller. The main criteria for me right now with in order is PC/serial communications, ADC and expandability. Expandability will be reading, sending signals to actuators.
http://www.microchipdirect.com
DM240001 – Explorer 16 Demo Board – $130
The Explorer 16 Development Board is a low-cost modular development system for Microchips new 16-bit microcontrollers. It supports devices from the PIC24F, PIC24H, and dsPIC33 families. It is capable of interfacing with 5V peripherals and also provides basic generic functionality with the added ability to expand to vertical markets via modular expansion.
MA320001 – PIC32MX 100P QFP TO 100P PLUG IN MODULE – $25
This Plug-in Module enables PIC32 development on the Explorer 16 development board (DM240001 or DM240002) and supports the MPLAB Real ICE Trace kit (AC244006). A 72 Mhz PIC32MX360F512L with 512 KB of Flash, 32 KB of RAM, 4 channels of hardware DMA and instruction trace is installed on the plug-in module.
