A hybrid linear actuator based on screw clamp operation principle: Design and experimental verification

This paper presents a hybrid linear actuator using screw clamp operation principle. The actuator mainly consists of a hollow electromagnetic torque motor located between two clamping nuts, two hollow cylindrical shaped piezoelectric stacks symmetrically configured at two ends of the actuator and a feed-screw (also considered as the mover of the actuator) assembled throughout all the parts. The torque motor is symmetrically connected to two clamping nuts via two torsion coupling springs located at either end of the motor spindle. Two piezoelectric stacks can work independently to propel the opposing loads, which effectively take advantage of the anti-compression and non-tensile characteristics of piezoelectric element. The special feature of the actuator is the screw clamp mechanism, the operation of which involves intermittent rotation of two nuts (driven by the torque motor) on a feed-screw to achieve the bi-direction piezoelectric motion accumulation. Furthermore, the application of feed-screw could decrease the actuator’s sensitivity to wear, in order to realize a rigid self-locking and thus ensure the actuator’s holding capacity. A prototype was fabricated and the experimental results show that the no-load speed, maximum thrust, and peak power of the actuator were 20 mm/s, 280 N, and 1.54 W, respectively.

Extrusion of wheat semolina and cocoa shells

Extrusion of wheat semolina and milled cocoa shells using a single screw extruder Brabender 20DN was carried out. Full factorial experiment 23 was used to investigate the effect of the quantity of cocoa shells, moisture of the material and temperature of the matrix on the density and expansion index of extrudates. Feed screw speed and screw speed were fixed at 30 and 200 rpm, respectively. Compression ratio of the screw was 4:1. Expansion index values range between 2.0 and 3.36 and a density between 0.099 and 0.223 g/cm3. The increase in moisture content and quantity of cocoa shells leads to a decrease expansion index, while density of extrudates an increase.

Effect of selected parameters on sectional expansion index and bulk density during the extrusion of chickpea instant semolina

A four-factor Response surface methodology central composite rotatable design was used to study the effect of moisture content, barrel temperature, screw speed, and feed screw speed on sectional expansion index and bulk density during extrusion of chickpea instant semolina for the purpose of instant product. The regression models for the investigated responses were highly significant (according to P-value) with satisfactory coefficients of determination (R2) 0.894 and 0.957. These results show that the predicted models for the investigated responses are adequate, indicating that the second-order polynomial model could be effectively used to represent the relationship between the selected parameters. The study showed that the expansion was influenced by moisture and temperature and it increased with increasing temperature for moisture content from 20 to 23% and after that decreased. Bulk density decreased with increasing feed moisture and barrel temperature in the extruder. The most important consequences for the science and practice resulting from the conducted research are that the resulting extrudates after grinding can be successfully used for the preparation of instant product with good characteristics, such as bulk density and sectional expansion index.

Velocity Control of Visco-Elastic Materials Movement in the Cylindrical Channel of the Grinder Feed Screw of the Former

The present research features the problems of wheat processing. Wheat processing has its own specific features. For instance, the process of gluten extrusion forming is very complex since it is associated with the visco-elastic and adhesive properties of raw gluten. The article discusses the results of applying the numerical finite difference method to the Navier-Stokes equation in the case of the one-dimensional problem when a cooled viscoelastic material has to pass through circular nozzles. The paper also features the obtained surface model of velocity evolution and some averaged results for the possible automation of the process. The viscosity properties of raw gluten are variable and depend on temperature, chemical composition, and properties of the raw material. Modeling makes it possible to characterize the properties of the material and its behavior in various situations. Such research demands neither additional time nor significant costs. The authors identified patterns of movement for raw gluten in the extrusion molding unit and selected the most appropriate automation system to control the speed of its movement to the molding assembly in the grinder feed screw. The significance of the research is obvious for subsequent physical and mathematical modeling of heat and mass transfer processes of vacuum freezing and drying and granulating of gluten extrusions. The results of the research presented in the article are consistent with the available information on this topic. The present approach to solving the problem of choosing the best rational hydrodynamic regimes was applied due to the complexity of the experimental determination of velocity fields and the difficulty of analyzing the Navier-Stokes system of hydrodynamic differential equations with variable proportionality coefficients.

Physical characteristics of extrudates from corn semolina flavored with cocoa shells

Extrusion of corn semolina milled with cocoa shells using a single screw extruder “BRABENDER 20 DN” was carried out. Full factorial experimental 22 was used to investigate the effects of the quantity of cocoa shells and moisture of the material on the water absorption index (WAI) and water solubility index (WSI). Working screw speed and feed screw speed were fixed at 200 and 40 rpm, respectively. Compression ratio of the screw was fixed at 4:1. Temperatures of the first, second and third zone were 150, 155 and 160 °C. Water absorption index values range were between 6.71 and 7.6 g/g and the water solubility index between 25.38 and 35.33 %. The increase in moisture content and quantity of cocoa shells leads to an increase in water absorption index and a decrease in water solubility index. Practical applications: Cocoa shells in an amount of up to 10% can be used in the production of extrudates by mixing with corn semolina. Water absorption index values range between 6.71 and 7.6 g/g and the water solubility index between 25.38 and 35.33 %. The resulting regression models can be used to optimize the process. In general, results show that cocoa shells can be mixed with corn semolina for the production of extrudates, which allows us to recommend extrusion processing of cocoa shells as an alternative technology in utilization processing of raw cocoa materials.

Three-Fingered Robot Hand with Gripping Force Generating Mechanism Using Small Gas Springs - Mechanical Design and Basic Experiments –

This paper presents the mechanical design of a new three-fingered robot hand for a robot designed to handle tableware. The finger mechanism has three joints and consists of a pair of fourbar linkage mechanisms, one small gas spring, and one feed screw mechanism. As the feed screw moves, the finger mechanism performs flexion and extension operations with its joints interlocked. The gas spring generates gripping force, which is adjusted at the position of the moving part moved by the feed screw. Therefore, the three-fingered robot hand can open and close synchronously, powered by a single motor in the base of the hand. The hand grips with mechanical flexibility. In addition, it can maintain its grip with no power supply. Tests show that the hand can successfully perform the movements required to grasp various kinds of tableware.

Development of Upper-Limb Power Assist Machine Using Linkage Mechanism – Drive Mechanism and its Applications –

This paper proposes an upper-limb power assist machine driven by a single actuator to reduce the weight and cost. This assist machine is used to support the shoulder and elbow movements for viticulture operations, and upper-limb holding for load transport tasks. This assist machine consists of an arm part and a mounting part. The arm part is composed of a parallel link mechanism, which is driven by an actuator and a trapezoidal feed screw. To realize a natural upper-limb motion, the length of the arm part was designed based on the human upper-limb motion. The assist machine is controlled based on the user’s intention by applying bend sensors attached to the input device. By measuring the electromyography signal of five muscles, the effectiveness of the proposed upper-limb power assist machine was verified experimentally.