Resource Reports
By: Anh Tram Do and David Gonsalez
A number of aspects are pivotal to the success of the Hexapod. Given that servos have a limited torque and the Hexapod will be running off a battery, we will have to budget both the weight of the build and the amount of current available for all the on board electronics.
Weight Distribution
From trade-off studies done which are illustrated in both the blog posts, we have concluded that our servos will be able to easily lift at least 10kg-cm. With our tripod gait, which we discussed in the trade-off studies, the servos will be responsible for 1/3 the weight of the body. Three servos will be working together to lift the body of the Hexapod, and hence the total force applied will be 30kg-cm. We have an estimate of a 70mm leg length or 7cm servo horn, which translates to 4.3kg of force from the combination of three servos.
|
Item |
Grams |
Newtons |
| Arduino ADK |
34.9 |
0.342 |
|
Adafruit Servo Shield (2) |
18 |
0.176 |
|
Tower Pro MG995R (19) |
1045 |
10.25 |
|
Battery Pack (Estimate) |
168 |
1.65 |
| Full Body |
196 |
1.922 |
| Android Phone |
133 |
1.304 |
| Scanning Platform |
100 |
.980665 |
| Total: |
1694.9 |
16.6187 |
Our force resource falls at 4.3kg, and our full weight estimate for the total build is 1.7kg. By this estimate we will have enough torque to easily lift the body of the Hexapod with a 2.6kg weight margin.
Current Allocation
Currently there is an ongoing study as to which battery we will be using. We have not finalized the resource allocation for current, but we have defined the early estimates of how much current most of the components draw.
|
Item |
No Load Current |
Minimum Current |
Max Load Current |
Average Current |
|
Arduino ADK |
TBD |
TBD |
TBD |
TBD |
|
TowerPro MG995 Servo (3) |
.33 |
.66 |
1.50 |
.66 |
|
Adafruit Servo Board (3) |
.025 |
.025 |
.025 |
.025 |
|
Android Phone |
TBD |
TBD |
TBD |
TBD |
These values are still preliminary. We haven’t finalized our coding, and have not completed testing all the servos in unison. When we have the code completed and all the servos assembled, we will be able to get an accurate reading of the current draw. At that point, we will know if we have enough power in our batteries or if we need additional power sources.
