Analysis and Testing

           In this section, several different aspects of the project will be discussed: power consideration, torque analysis and cleaning area.

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Power Consideration

            Power consumption was calculated before the mid semester. As shown in Table 1, the power consumption of each electronic part was listed. The reason why only 50% of running time is considered for linear servo, valve, and servo is that only half of the parts are actuated during the motion. Raspberry Pi was also considered in this table in case a replacement is needed. The total amperage draw is 3.05 A. The battery capacity needed is 400 mAh if the operation time is 5 minutes.

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Table 1: Power consideration

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Torque Analysis

           Torque is also a crucial part in our analysis. The stall torque should be higher than the torque needed to rotate the entire robot. According to Figure 1, the stall torque of the RC servo is 43 kg-cm, which is 37% higher than the torque demanded. The torque analysis proved that our RC servo should have the ability to complete the rotation motion on the window.

 

 

 

 

 

 

 

 

 

 

 

 

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Figure 1: Torque Demand vs. Torque Available

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Cleaning Area

           The cleaning area has been changing with the design. Figure 2 shows that the first design of the robot had a poor performance. The cleaning area is much smaller than the motion range. After the second major modification, the side cleaning area was significantly enlarged while the top cleaning area was still small. After consideration, the motion pattern was changed so that only side and bottom area are cleaned during each motion.

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Figure 2: Cleaning Area vs. Motion Range diagram

 

 

Performance Evaluation

            The overall performance is not ideal at the end of the semester. Some tests showed that the robot is capable of performing the planned motion pattern and transition on the window. However, the performance was not stable. Due to the noise issue caused by the pump, other electrical components had jittering problems. The barrier-crossing motion cannot be performed at the end of the semester.

 

 

Strong and Weak Points

            There are several strong points for the Window Monkey. The overall system does not generate much heat, which reduces the complexity of the design. The robot also has a novel motion design compared to other traditional designs. The entire system is relatively quiet compared to fan mechanism. The robot should be able to finish the task in time if all problems are solved.

            The weak point of this robot is that some subsystems require very intricate design. For example, the linear actuating arm has been modified several times during this semester. The first two designs were too fragile and sometimes not actuating in the correct direction.

            Another weak point is the noise issue. The noise generated by the pump affected the entire system during the semester. Although it was mitigated at the end, the problem still existed, which caused some unnecessary vibration and power consumption issue.