mobility performance evaluation of planetary rover with simi(3)

月球车珍贵资料——来自美国

L′L=

g T′gF′,T=gg α′′,α

=g′g , V′

V=1 F′Gg2

3

HI Mr′FgF=

g′,Mr=GHI

g′

When the moon is the target of exploration, gravitational acceleration of the moon is 1/6 of that on the earth. Therefore, in the experiment under 1G gravity, an expression of relations can be found as follows:

L′L=16 T′, T=16 , V′

α′V=1 ,

α=6

F′F=1

36 Mr′=1, Mr216

In the experiment under 1/2G gravity, an expression of relations can be found equally as follows:

L′1

T′α′L=3 , T=13 , V′V=1 ,

α=3 F′F=1

9 , Mr′Mr=127

That is, in the gravitational acceleration that experiments, the suitable experiment model is required.

V. Model Experiment A. Similarity Models

Using an experimental model, we measure the velocity, the number of rotations of a wheel and the gradability, etc. We would make relative evaluation on degree of mobility according to several systems. Therefore, we'll construct the similarity model, which has the above-mentioned typical mechanism.

In fact, we have produced two similarity models that have 4WD system and PEGASUS system. One side is the model (shown as '1/6 Model' hereafter) for 1G gravity, another side is the model (shown as '1/3 Model' hereafter) for 1/2G gravity. We have been cautious of the following points when we design and produce a model.

(1) The origin of an experimental model is next generation of exploration rover called "M5A". We would advance a project, striking a balance between the origin and the model.

(2) An experimental model is equivalent to original model in mass, the position of the centroid, and an inertia moment. (3) An experimental model has adequate strength and simple structure.

(4) Effective dust-proof countermeasures, e.g. silicone coating etc., on experimental models are taken to carry out ex-periments on sandy surface.

The small and light weight brushless DC motor is used especially in the 1/6 Model. In order to control the number of rotations of a motor, we have designed the drive circuit board. Then, we can set up widely and safely the velocity of an experimental model.

The 1/3 Model has SH2 CPU board, an interface board, a PWM driver board, and a supply circuit. CPU board controls the DC motor freely.

The resin, e.g. ABS etc., is used as the material of the experimental models, in order to realize weight saving, having adequate strength.

We have successfully produced an experimental model, which fills a similarity law. Figures 5 and 6 show the overview of the model used in the experiment. The specifica-tion of a model and original is shown in Table 1.

Fig.5 1/6 Model Rover for 1G gravity

Fig.6 1/3 Model Rover for 1/2G gravity Table 1 Specifications of a Miniature Rover & Micro5

B. Low-Gravity Flight Experiment

First of all, we have carried out the low-gravity flight examination using the 1/3 model on the airplane. In this experiment, parabolic pattern flight (shown in Fig.7) by airplane provides around 20 seconds of micro gravity condition in the cabin. We have following merits in the aircraft micro gravity flight.

- Can provide many G level conditions (+0.03G to 2.5G) - Provide many chances of experiment in one flight operation