4. Discussion

4.1 Analysis of results


Motor type
Usage
Purpose
Results (Did it work?)
HITEC HS-815BB
Base rotation
Turns 180°
HITEC HS-755HB
Shoulder bending
Turns 90°
HITEC HS-755HB
Elbow bending
Turns 90°
HITEC HS-311
Wrist rotation
Tilts 45°
HITEC HS-5070MH
Claw grabbing
Tilts 45°

4.2 Key findings


The robotic arm can pick up a weight of up to 20 grams. This shows that the arm is suitable for picking up small rocks or chemicals.


The motors were able to be connected and worked successfully. However, we were faced with another challenge. The parts on the elbow onwards which includes the elbow, wrist and claw, are too heavy to carry themselves.
We have therefore failed to meet one of the specific requirements which states that the robotic arm has to allow the user to be able to pick up unidentified objects safely and not to put him/her at risk.


We tested out each part individually by powering the circuit and turning the potentiometers one by one. Each part was able to move efficiently and no parts were falling apart. The elbow was able to move as well except that it needs external support to hold its weight.


The robotic arm can withstand mild temperatures and conditions such as heat from a hairdryer, wind from a fan, etc.


The motors are able to move efficiently and turn their required parts, therefore, this will make it easier for users as they would have no issue in time consumption.


4.3 Explanation of key findings


The robotic arm is not suitable for doing heavy lifting but is suitable for more precarious uses such as picking up some rocks or test tubes for experimental purposes. These uses keep the user from danger if the chemicals are dangerous.


The base motor is effective in turning the arm 180 degrees back and forth to collect or place the item. The elbow motor is effective in turning the arm 90 degrees down to collect the item.However from the elbow to the claw,the arm drooped.
IMG_7370.JPG
As seen in the diagram above,
-The perpendicular distance B is greater than the perpendicular distance A
-The force acting on the elbow for B is therefore significantly larger than the force acting on the elbow for A.
Therefore, the clockwise moment will be greater than the anti-clockwise moment
Clockwise moment of the arm=/= Anti-clockwise moment of the arms
Thus, the arm will not rest at equilibrium.


Another reason to why the arm was drooping could be due to the type of motor we used. We were originally planning on using the servo HITEC HS-755HB motor for the shoulder. However, we realized that it was too heavy for the base to carry. Therefore we replaced the shoulder motor with a servo Tower pro 646WP which is not as strong as the previous servo motor. Because we replaced the shoulder motor with one of less strength, it resulted in the shoulder not being able to support the elbow, wrist and claw, thus, the upper portion of the robotic arm droops.


As we turn each potentiometer, the required part turns efficiently and does not drop out. This proves that the programming of the arduino is correct and accurate. This also proves that the parts were secured properly.


4.4 Evaluation of engineering goals


Did we meet our engineering goals?
  • To create a device which is able to pick up unidentified objects which could have harmful substances present thus, keeping the user safe and out of harm’s way.
  • To create a device which aids students and teachers in science lessons which involve the use of radioactive/infectious chemicals, thus, keeping the user(s) safe


4.5 Areas for improvement


We could make the claw easily removable so that the user could change the claw design whenever he/she wanted to for different purposes.


The materials for the arm could be made lighter so that the base can be stable without securing it to the ground or table. In a similar project which requires to build a robotic arm, the product which is called Exatech, the total weight of the robotic arm is approximately 4KG and functions without problems. They used aluminium to build their robotic arm. Our robotic arm weighs <insert weight> and uses acrylic sheets with a thickness of 3mm.


We could reconsider the sizing and measurements of the robotic arm. In our project, the upper portion of the arm was too long, thus, it drooped. The weight of the motors also contributed to the arm drooping as the clockwise moment was greater than the anti-clockwise moment.

The shape of the claw could be redesigned and re-considered to be more suitable for picking up objects with indefinite shapes. The claw could also posses a better grip to ensure that the item will not fall easily and the user will be more assured of his/her safety.

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