GENERALIZED CRITERIA FOR LOADING CAPACITY OF INDUSTRIAL ROBOTS

The analysis of the correspondence of the set of functional indicators of industrial robots to the criteria of criteria similarity conditions is carried out. Using the methods of the theory of dimensions, criteria for the similarity of the functional properties of carrying capacity, speed-action and dynamism of industrial robots in terms of rotational and translational degrees of mobility have been determined. The necessary set of criteria has been created and a concept has been proposed for determining the generalized criterion complexes of the load capacity for modules, aggregates and the entire structure of the robot as a whole using the method of defragmentation and averaging the corresponding criteria by degrees of mobility. The proposed performance criterion makes it possible to compare the performance of a group of robots in terms of three kinematic indicators: speed, acceleration and the range of permissible displacements. For robots of light load capacity, the technical evolution of the considered criterion complexes is presented. It is noticed that with an increase in the reach of the robot, the criterion of load-carrying capacity for all robots decreases. The developed criteria make it possible to assess the speed action and loading capacity of a robot of any design and can be used to determine the technical level of robots and identify reserves for increasing it. Key words: degrees of mobility; manipulation system; homogeneous functions; dynamic parameters

Second-Law Analysis of a Double-Effect Evaporator with Thermal Vapor Compression

In this paper, we present a steady-state analysis of a double-effect evaporator with thermal vapor compression (MED-TVC) installed in the Tunisian Chemical Group (GCT) factory. A thermodynamic model including mass and energy balances of the system is developed and integrated in a Matlab program. The model resolution yields to the determination of the operating parameters of the plant and the Gain Output Rate (GOR) was found to be roughly equal to 5. In a second step, the simulation results served to conduct a second law analysis of the unit. The performance criterion used in this analysis is the second law efficiency, i.e., the ratio of the least theoretical work of separation to the actual work input to the plant. The second law efficiency was found to be 2.4%. The distribution of the irreversibility between the different components of the plant was, in addition, assessed. As a conclusion, it was established that the most irreversibility occurs in the thermo-compressor which contributes with more than 50% to the global imperfection and which presents an exergy efficiency of less than 77%. The remaining irreversibility comes from the three exchangers (the two evaporators and the condenser) with an average contribution of 16%. As it is very difficult to introduce modifications into an existing unit, we assume that the importance of the results is not limited to the studied unit. They serve, rather, as an aid to the future design of a MED-TVC plant.

Spaced training enhances equine learning performance

This field experiment examined whether the well-documented benefit of spaced over massed training for humans and other animals generalizes to horses. Twenty-nine randomly selected horses (Equus ferus caballus) repeatedly encountered a novel obstacle-crossing task while under saddle. Horses were randomly assigned to the spaced-training condition (2 min work, 2 min rest, 2 min work, 2 min rest) or the massed-training condition (4 min work, 4 min rest). Total training time per session and total rest per session were held constant. Days between sessions (M = 3) were held as consistent as possible given the constraints of conducting research on a working ranch and safety–threatening weather conditions. During each training session, the same hypothesis-naïve rider shaped horses to cross a novel obstacle. Fifteen of 16 horses in the spaced-training condition reached performance criterion (94% success) while only 5 of 13 horses in the massed-training condition reached performance criterion (39% success). Horses in the spaced-training condition also initiated their first obstacle-crossing faster than horses in the massed-training condition and were faster at completing eight crossings than horses in the massed-training condition. Overall, task acquisition was higher for horses undergoing spaced training despite both groups experiencing the same total work and rest time per session. These findings generalize the learning-performance benefit observed in human spaced practice to horses and offer applied benefit to equine training.

Improving the efficiency of the steganographic method of data hiding with the application of iterative functions and noise addition

The development of computer and digital technology contributes to the growth of information flows transmitted through open and closed communication channels. In many cases, this information is confidential, financial, or commercial in nature and is of value to its owners. This requires the development of mechanisms to protect information from unauthorized access. There are two fundamental areas of secure data transmission over the open communication channels – cryptography and steganography. The fundamental difference between them is that cryptography hides from others the content of the message, and steganography hides the very fact of the message transmission. This paper is devoted to steganographic methods of data concealment, which are less researched than cryptographic, but have significant potential for use in a variety of applications. One of the important characteristics of most methods is their effectiveness. In general, efficiency is assessed in the context of solving specific problems. However, the most common criteria for the effectiveness of steganographic methods are the amount of hidden data and the method of transmitting the secret key to the receiving party, which will not allow the attacker to intercept it. Because media files make up a significant portion of network traffic, a digital image is chosen as the stegocontainer. It is proposed to determine the coordinates of the embedding location on the basis of iterative functions. The advantage of their use is the compactness of the description of the coordinates of the pixels in which the data will be hidden. In addition, it is proposed to use the Diffie-Gellman algorithm to transfer the parameters of iterative functions to the receiving side. This method of key distribution makes the steganographic method less vulnerable to being stolen by an attacker. The second performance criterion is the amount of hidden data. The paper found that the moderate addition of multiplicative noise makes it possible to increase the amount of hidden data without significantly reducing the visual quality of the stegocontainer. To analyze the distortions in the image-stegocontainer, which are due to the influence of noise and modification of the lower bits of pixels, the method of a quantitative assessment of visual quality is used, which is based on the laws of visual perception. Keywords: steganographic data hiding; hiding efficiency; iterative functions; Diffie-Gelman algorithm.

PID-based with Odometry for Trajectory Tracking Control on Four-wheel Omnidirectional Covid-19 Aromatherapy Robot

Inhalation therapy is one of the most popular treatments for many pulmonary conditions. The proposed Covid-19 aromatherapy robot is a type of Unmanned Ground Vehicle (UGV) mobile robot that delivers therapeutic vaporized essential oils or drugs needed to prevent or treat Covid-19 infections. It uses four omnidirectional wheels with a controlled speed to possibly move in all directions according to its trajectory. All motors for straight, left, or right directions need to be controlled, or the robot will be off-target. The paper presents omnidirectional four-wheeled robot trajectory tracking control based on PID and odometry. The odometry was used to obtain the robot's position and orientation, creating the global map. PID-based controls are used for three purposes: motor speed control, heading control, and position control. The omnidirectional robot had successfully controlled the movement of its four wheels at low speed on the trajectory tracking with a performance criterion value of 0.1 for the IAEH, 4.0 for MAEH, 0.01 for RMSEH, 0.00 for RMSEXY, and 0.06 for REBS. According to the experiment results, the robot's linear velocity error rate is 2%, with an average test value of 1.3 percent. The robot heading effective error value on all trajectories is 0.6%. The robot's direction can be monitored and be maintained at the planned trajectory. Doi: 10.28991/esj-2021-SPER-13 Full Text: PDF

Computer Aided Cylindrical Spur Gear Design

Spur gear is used in machines to transmit rotary motion. Due to its simple design, reliability and compactness, it is widely used in technical devices — clocks, conveyors, cars. Two wheels of such a transmission have a constant gear ratio and high efficiency. The first performance criterion is the contact stress fatigue strength of the teeth. The second one is the tooth bending fatigue strength. Manual calculation of a spur gear is a difficult task due to the large number of formulas and conditions. The design area is limited to a small number of options that are not always optimal. It was proposed to expand the design boundaries to hundreds or thousands of options using a computer. Combinations of parameters (modulus, wheel width, number of teeth, material, etc.) form a variety of spur gears with different characteristics: dimensions, strength, weight, etc. The statistical analysis found hidden dependencies between characteristics and initial parameters. On the basis of regression metamodels, the relative importance of parameters for individual characteristics was established. When searching for optimal gears, the Desirability function D was applied with meta-models as arguments. On the basis of the existing standards, a system for computer-aided design of transmissions and statistical analysis of their performance has been developed. As a result of the study, the area of efficient spur gears with optimal characteristics was determined.