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The second requirement is the mobile platform mass minimization. To fulfill this requirement it is important to use cylinders with minimum possible diameter. These cylinders also allow to air economy, which is important not only for mobile robots [2]. Current robot model uses the cylinders with piston diameter of 50 mm thus weight of
mobile platforms is 30 kg and 70 kg. The ratio of required movement time (average speed), object mass and the cylinder diameter bring a problem of safe braking in the end of the stroke. It is determined that the speed of massive objects in such tasks makes oscillation while the piston is running [3]. Therefore the dynamic forces in the movement process can be great, so piston with connected object can reach the cap without controlled speed and cause the shock, which could lead the separation of suction pads from the surface and falling of robot. It is visible that the requirements of the increasing and minimizing of dynamic forces are inconsistent. Implementation of drives requirements is difficult in these conditions.
STANKIN experience in using of standard pneumatic cylinders with integrated braking system tells that they aren’t match for such kind of tasks in VMMR. These braking systems allow isolating the volume with compressed air in the end of the stroke and exhausting the air through the throttle tight in right way. The disadvantage of such systems consists in appearing of large dynamic and shock loads caused by very intensive braking, especially if the braking direction aligns with the gravity direction.
The conducted researches tells that the solving of such task consists in creating the structure of electro-pneumatic drives as a mechatronic systems, equipped with valves, throttles, sensors and microcontroller. There are two possible approaches to the problem of control of the pneumatic actuator. The first one is based on the use of proportional valves and continuous control laws. The implementation of this approach uses a proportional-integral regulators and may require non-linear control laws and technology of intelligent control [5, 6, 7]. The second approach is based on the use of on-off valves and discrete control laws that implement multistage braking. Its implementation is less expensive, because of on-off valves that are very simple, reliable and cheap [3, 4] in comparison with known solutions that contain proportional valves. Thus, it is obvious that for creation of discrete pneumatic drives of such kind’s mobile robots the second approach is more preferable.
These electro-pneumatic drives represent sophisticated non-linear dynamic systems. Developing of such kind of systems requires detailed mathematical models and computer simulating programs that represent the effective instrument for analysis of properties of VMMR. The special attention in this article is paid to computer simulation of high-speed mechatronic electro-pneumatic drives for VMMR. It is necessary to note that these researches were financed by Ministry of Science of Russia Federation within the state task in the sphere of scientific activity.
2. The structure of high-speed mechatronic electro-pneumatic drive for massive objects with high smoothness of movements
It is offered to create the electro-pneumatic drive with computer control and position feedback for high-speed and smooth movement of VMMR’s mobile platform. The structure of such drive is shown at Fig. 2. The drive is aligned the principles of mechatronic. This design gives the following advantages:
● high speed of the massive object
● limit dynamic loads in the process of movement by realizing of multistage braking at the end of the stroke
This drive of VMMR is more complex than the standard cyclic drive. But the use of this drive is reasonable for reaching the higher quality values, which can be achieved by fusion of more complex hardware executive part and software of the mechatronic system.