******************************************************************* *** *** *** *** *** DIALY LOGS - NALAKA KAHAWATTE *** *** *** *** February, 2007 *** *** *** ******************************************************************* ******************************************************************* Tuesday 2/06/2007 3.00 - 5.00 pm As Dr. J suggested, i did studies on the PYRO. for software and tutorials check ( http://pyrorobotics.org/ ) Important*** PYRO can be used for the Sony AIBO and There is also a simulator available for Robocup soccer. I will further read the tutorials and add my findings, -------------------------------------------------------------------------------------------------------------------------- Wednesday 02/07/2007 2.15 pm - 5.15 pm Soldered the power supply from the existing controller board to the breadboard and fixed the connections. Shane and I worked on using input signals to the motor-driving-microcontroller ( which we plannin on sending from the co-proocessor ). Please refer to Shane's Logs for detailed information. ---------------------------------------------------------------------------------------------------------------------------- Thursday 02/08/2007 11.30 am - 3.30 pm ATV Inspection : 1. Steering System I suggest using a stepper motor and mounting on the position where the rotating steering rod meets stationary rod. Please refer to pic1.jpg. I stepper motor is more effective than a servo for the following reasons. I. Stepper can produce more torque which we need to steer front wheels. I will measure the minimum, suggested torque needed to turn the wheels and get details of stepper motor required. II. Unlike Servos, Steppers can be used in a open-loop control system. where we do not need a feedback system to know the positioning of the motor, since stepper motor works on pulses and for each pulse it turn a specified amount of degrees. By keeping track of number of pulses we can know its position. So an optical encoder is not necessary. III. stepper is meant for more precision movements than servos. **** Torque calculation for steering ****** Using a Spring Scale, ( on Newton Scale ) i estimated the force needed to turn the wheels. According to my calculations. On the polished surface, 4.8 Nm torque was needed to turn the wheels. If my assumption is correct, ( let's verify it on a rough gravel surface ) im assuming a maximum of 15 Nm torque should comfortably turn the wheels on a rough surface which the Hummer is intended to. I would like to get the Hummer out to a Grass Field and test it. cos it will need more torque there. IMPORTANT ! Some Stepper Motor specification sheets have indicated the torque measurements on oz-in scale. For easier conversion to Nm scale. 1 Nm = approx. 140 oz-in I think we should be looking at a stepper motor with around 15 Nm ( approx - 2000 t0 2500 0z-in ) torque. Since, I believe the ultimate goal of hummer is search and rescue, goin for a higher torque motor would be a better investment. 2. Braking system I took out the encloser for the breaking system. Please refer to pic2.jpg Its a disk break system. The cable tension moves the brush which applies breaks to the disk. Idea : Use a small stepper/servo and to connect the cable to it. the motor should pull the cable only about 2cm max for the breaks. again, i think a small stepper should work. 3. Acceleration / speed. Idea : Refer to pic3.jpg I suggest using the existing variable resistance method at the handle. This will be a better method to control the speed. at the moment, i get ideas on the line of a motor. again, use a small stepper to emulate the motion of the movement, when we want to accelerate. 4. Mounting the controllers Im thinking of mounting the controllers on top of the power source. Refer pic4.jpg with a small encloser from either side. -------------------------------------------------------------------------------------------------------------------------------------- Thursday 02/15/2007 10.00 am - 12.00 noon & 12.30 pm - 4.30 pm I brought two good books on similar types of projects called MOBILE ROBOTIC CAR DESIGN an PDA ROBOTICS which i've kept on the shelf. They both walk thru the steps on similar types of projects and it has good information. I went thru that material and found some important points which we can incorporate in our hummer. 1. Rewiring the motor to reduce speed and increase torque Refer to MOBILE ROBOTICS CAR DESIGN - page 27 it walks thru the steps for the process. 2. in PDA Robotics, it talks about how to set up a IRDA connection to the robot to control/steer/program which may be useful for us since we are expecting to incoroprate WiFi feature. 3. Using a Digital Signal Processor for streaming data, such as video, audio, rf reciever. Please check 'IDEAS -LOG' for more info. 4. For future use, i found this company which does custom 2 layer printed circuit boards for only $33. No minimum quantity. check out the link. http://www.4pcb.com/leadfree_stencils_engineering_student_program.htm it'll be so much easier for us if we could get this going. it'll reduce the hassle of wiring. and we can move forward with higher pace. I will read more on how to get the PCBs done. ---------------------------------------------------------------------------------------------------------------------------------- Monday 02/19/2007 2.45 pm - 5.45 pm Read more on the Mobile Robotics Design Book. Took out the restrains for turning. Shane and I brain stormed ideas on way to mount drive motor on the handle. --------------------------------------------------------------------------------------------------------------------------------------- Wednesday 02/21/2007 2 pm - 3 pm 4 pm - 5.50 pm 6.00 pm - 7.00pm eATV/Hummer Team Meeting. collected ideas for different components to be implemented on the eATV. Please refer to Mike's logs for further details. ISL group meeting. ---------------------------------------------------------------------------------------------------------------------------------------- Thrusday 02/22/2007 2 pm - 5.30 pm Shane and I drafted different ideas and methods of steering the eATV. Hot Wired the starter plug together so that the eATV has connection to the power. now it does not have a ON/OFF switch. it jus takes off when u throttle is up. -----------------------------------------------------------------------------------------------------------------------------------------