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.