Screw-nut Mechanism Research Articles

Modeling and Experimental Validation of the Performance of Electromechanical Height Adjustment Vehicle Suspension with Eccentric Mounted Screw System

This paper describes the modeling and experimental validation of the performance of two height adjustment suspensions with concentrically and eccentrically mounted screws. In the former solution, an anti-rotation system is required for the generation of reaction torque on the power screw–nut mechanism. The anti-rotation represents the main drawback of such mechanisms. In contrast, the eccentric solution attempts to solve this problem by placing the screw–nut mechanism eccentrically with respect to the shock absorber tube axis. In this paper, the working principle of the eccentric solution is explained. Its performance is compared to the concentric counterpart through simulations and experiments. Although the efficiencies of eccentric and concentric systems are very similar at the power screw, overall efficiencies differ substantially. During lifting, average efficiencies are around 3.4% and 6.5% for concentric and eccentric systems, respectively. When lowering, these values are 6.2% and 26%. The higher overall efficiency of the eccentric screw system is attributed to the anti-rotation system and the balancing of the bending moment due to the offset application of the load. To yield a complete perspective on the eccentric mounted screw solution, four prototypes are installed and tested on a demo vehicle.

A wave energy harvesting system based on the double-wing flywheel for unmanned surface vessels

Unmanned surface vessels (USVs) are increasingly used in environmental protection, safe search, rescue, and maritime investigations. These USVs are generally battery or diesel-powered for sailing, and the limited size of USVs results in a lower working life of USVs. This paper proposes a wave energy harvesting system for USVs based on a double-wing flywheel. This system is installed in the hull of the USV and converts the wave energy that causes the USV to vibrate into electrical power. The system can be divided into four modules: wave energy capture module, motion conversion module, electromagnetic transducer module, and circuit module. The wave energy capture module captures the mechanical energy of USV vibration caused by waves and the change of driving state and converts it into the mechanical energy of the mass block vibration. The motion conversion module uses a screw-nut mechanism and the double-wing flywheel mechanism to convert the reciprocating vibrations of the mass block into the relative one-way rotation of the magnet flywheel and the coil flywheel. The electromagnetic transducer module converts the mechanical energy of flywheels into electrical energy and transmits it to the circuit module. The circuit module rectifies the current and stores the electrical energy in a supercapacitor, eventually used to power various sensors. Simulations and experiments were conducted on the proposed wave energy harvesting system. MTS bench experiments confirm a 51.64% increase in energy harvesting power than an energy harvesting device without a mechanical motion rectifier (MMR). Data transfer experiments show that the system can capture wave energy to drive temperature and humidity sensors for data transmission. The results show that the energy harvesting system can be practically applied to USVs to improve their service life.

A novel kinetic energy harvester using vibration rectification mechanism for self-powered applications in railway

Rail transit system has been considered to have a large energy harvesting potential, and to be usable to achieve self-powering for rail-attached electrical installations. Dowty retarder is a key device installed on the side of rails to assist train braking, which can be used as a carrier for kinetic energy harvesting. In this paper, a high-efficiency kinetic energy harvester (KEH) based on a railway Dowty Retarders (DRs) is investigated. This new KEH can accumulate the kinetic energy of a decelerating train using a novel vibration rectification mechanism. The current study comprises four main components: energy input module, motion transmission module, generation module, and energy storage module. The energy input module has a screw-nut mechanism that can convert linear vibration into rotational motion. As a core component of the entire device, the motion transmission module contains a special closed-loop shaped gear train that converts the two-way rotary motion into a unidirectional rotation. The final unidirectional rotation is transferred to the generation module for power generation and the generated energy is stored in the energy storage module. Finally, both experimental and simulation approaches were performed to verify the dynamics response of the KEH mechanism. The maximum efficiencies of 55.4% and 51.9% are obtained during the simulation and experimental analyses. It is validating that the KEH mechanism is promising and practical in self-powered applications for the heavy haul railway.

Design of Obstacle Avoidance Mechanism of Magnetic Levitation Type Inspection Robot for High Voltage Lines

An obstacle avoidance mechanism is designed for the operation mode and the overall structure of high-voltage power lines inspection robot based on magnetic levitation principle. The mechanism is composed of a planar linkage mechanism and a screw nut mechanism with two degrees of freedom. Through the control of two of the original, the robot has a function of opening the shell and obstacle avoidance. The mechanism is simple and occupies less space with flexible movement, compact structure, to meet the requirements of obstacle avoidance to avoid vibration hammer, clamp, straight line towers and other obstacles effectively which solved the contradiction between the small space in the robot and the obstacle avoidance requirements. Two prime bar linkage relationships is obtained according to static analysis of the mechanism. Finally, by means of Kinematics simulation of the obstacle process through Pro/E software, the feasibility of the institution obstacle scheme is verified.

Experience with Material Combinations for Sliding Applications in PFBR In-Vessel Fuel Handling Machine

Prototype Fast breeder Reactor (PFBR) is a pool type reactor of 500 MW(e) capacity using mixed oxides of Uranium and Plutonium as fuel and liquid sodium as coolant, which is currently under advanced stage of construction at Kalpakkam. In-Vessel handling of the core subassemblies (SA) is carried out by an offset arm type machine called Transfer Arm (TA). Different types of material combinations are utilized for various sliding pairs used in the machine for various motions. Criteria for the selection of these material combinations are decided by the compatibility of the respective machine element with the working environment, magnitude of the contact stress, working temperature, linear speed, availability of external lubrication, required life, required tolerance etc. Transfer of a SA is achieved by gripping/ungripping of SA using fingers, raising / lowering the gripper outer tube and rotation of TA. The drive for gripper finger operation is at ambient environment and finger actuation is in liquid sodium. An inner tube links the linear actuator to the finger actuator and is housed and guided inside the gripper outer tube. Relative movement of inner tube with respect to outer tube results in open / closing of gripper fingers. Initially, combination of material pairs at five nos. of guide locations was SS 304 LN for the outer tube and hardchrome plated SS 304 LN for inner tube. During testing in air after 20 cycles, jamming of inner tube with respect to outer tube was observed. This was solved by reducing number of guides to two, by changing the surface contact to line contact and by changing the material combination to SS 304 LN against colmonoy coated SS 304 LN. Similar failure was observed for sliding movement at guide locations between the outer tube and shielding sleeve during hoisting of the gripper. Initial material combination of SS 304LN and hardchrome plated SS 304 LN was changed to colmonoy coated SS 304LN and hardchrome plated SS 304 LN. The selected material combinations were validated by testing on a separate subassembly simulating the geometry & loading before actual implementation on the machine. Guide tube, which is used to guide the gripper is raised / lowered by means of a screw-nut mechanism. Initial material pair used for the screw and nut, which are working at ambient conditions was SS 304LN and SS 410 respectively to provide corrosion & galling resistance. However during initial performance testing, this material combination failed and the nut got jammed. Subsequently the problem was studied and overcome by changing the material of nut to phosphor bronze, which is relatively softer and hence provided uniform contact across the nut surfaces. Appropriate material selection and proper design of the geometry of guiding surfaces are very essential for the smooth operation of machine elements in sliding conditions. With improvements in the material choice and geometry of the guides, qualification testing of transfer arm was successfully completed in air and hot argon. Testing in sodium is under progress and the experience at high temperature has been encouraging.

Non-Contact Actuation of Less-Invasive Bone Lengthening Device Using Embedded Cycloidal Motor Driven by Permanent Magnets from the outside

This report proposes a miniaturized non-contact actuation mechanism for a surgical device for bone extension operation. The device is embedded inside the body, and the device controls the gap between the bones cut by operation. A small permanent magnet is attached to the outer gear of a cycloidal reducer that rotates a screw of the screw-nut mechanism. This magnet is forced by the external magnetic flux density controlled by the outer permanent magnets’ position. In this research, two pairs of permanent magnet bar were rotated by stepping motors outside the device. The outer gear is constrained in As a result, ring gear of the cycloidal reducer is driven in translational wobbling motion the inner gear is connected to the screw and the output nut position is driven linearly with screw rotation. The dimensions of the fabricated device were 7 mm in diameter and 39.7 mm in length. The output thrust of this device was 2 N.

Mechanical-Electronic-Hydraulic Integration: Light Load Linear Reciprocating Motion Device Having Variable Frequency, Displacement and Velocity

The light load linear reciprocating motion device driven by a small-size pneumatic cylinder is most economical, but its velocity and location precision is not good. When substituting the drive for small-size hydraulic cylinder, the significant shortcoming is environmental pollution. If the motion is achieved through rolling screw-nut mechanism driven by stepping motor, the space layout is very inconvenient. A light load linear reciprocating motion device integrating mechanical, electronic and hydraulic technology is designed. In this device, the motion is achieved through short-stroke rolling screw-nut mechanism driven by stepping motor, and then amplified by a splendid internal reflux area effect stroke amplifier. This device has the following noticeable advantages: (1) The location of output hydraulic cylinder is as convenient as common pneumatic or hydraulic cylinder. (2) The frequency, displacement and velocity of reciprocating motion can be altered convenient by programming. (3) Higher position precision. (4) The hydraulic fluid in the device is enclosed, so there is no environmental pollution causing by oil leakage and volatilization.

Ruling engine using a piezoelectric device for large and high-groove density gratings

A ruling engine for large and/or high-groove density gratings is developed. A hybrid driving method that uses a piezoelectric device and a screw-nut mechanism is adopted to achieve stop-and-go blank motion with a closed-loop control system. Several test gratings, including a ruled area of 300(width) x 200(groove length) mm(2), groove densities of 6000 and 10,000 grooves/mm, and a uniform and varied-line space, are ruled to confirm the basic functions of the ruling engine. A set of four spherical, varied-line-space gratings with central groove densities of 6000, 4550, 3450, and 2616 grooves/mm and a ruled area of 200 x 200 mm(2) is ruled for the orbital retrievable far and extreme ultraviolet spectrometer.