Dronesonen

Robot Arm – Week 2

This week we started individual work on different aspects of the project. We started testing different types of servos that were available to us in Dronesonen. Using example-code on an Arduino, it was possible to control servos using a potentiometer. The movement of each servo was a bit unstable and jittery. This could be because of the unstable resistance of the potentiometer and/or using the Arduino as a power supply.
A joystick is controlling two servos. One on the x-axis and one on the y-axis
First tests started using the ultrasonic sensor for determinig the distance of an object. The plan is to use it with the robot arm. also wrote some tests and custom functions using the LCD  so that we can use it later to display messages and results etc. Beside the electonics also the construction of the arm started. After the first handdrawn sketches the main part of the Arm was constructed in Fusion. An arm range of 40 cm (from joint to joint, so two times 20 cm) was considered enough to have enough flexibility in movement to cover up a whole sheet of A4 or A3, but with few limitations in the Z axis. The 3rd servo was positioned at the upper joint to simplyfy the overall design. The choice of materials will be a mix of lasercut plywood (light-grey) and 3d-print (plastic) (green).
First CAD construction of the robotic arm

Machine

At our meeting 08/09 the group decided to put down some parameter for our design.  By drawing up the size for our gameboard we ended on an arm around 20cm. since our primary goal was to make an arm that could play “tic tac Toe” we wanted the parameter to be reflected in this.We also sat 4 joints in our design so that we could maneuver our arm more freely. This could also come in handy later if we wanted to expand on our hands function and use.

By doing a quick sketch in Solidworks the group got a overview of the arms mobility.

Figure 1: sketch from solidworks

After finding an example of an arm on the internet. We decided that it would be cool to hide the electrinical component. Referring to Fig 2 we see that the electronics in the back are hidden. Making the arm look more whole.

Figure 2: Kilde:  https://www.trossenrobotics.com/widowx-250-robot-arm-6dof.aspx

I also took some measurement from the servos we were planning to use so that when I started to design, I could place the servos directly into the design. I also took the names and number so that I could later find the specifics for the different servos and do some calculations for strength.

Problem! 

We were planning on using a vacuum suction cup at the end of our arm, but the school did not have vacuum pump. therefore, will have to build one or go for another solution. Electromagnet was discussed. But we have to look a little bit closed on this. Buying a pump where not an option due to price of kr 2000,- for one pump.

Homework for next time machine will start on the design and primary on the board. This was so data could do test on the board. I will also start and try to come up with a more specific design that includes necessary strength, built in components, the primary goal for our arm and figure our how our joint could move the most smoothly.

Electro

we have designed a circuit for the electronic part and calculated how big the battery should be and  we end up with  2* 9V batteries, and for the servos we will be using 3 tower pro mg995  and one Towerpro SG90 9g mini servo.

Robot Arm

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