Design and experimental evaluation of a new modular underactuated multi-fingered robot hand

© IMechE 2020. In this paper, a modular underactuated multi-fingered robot hand is proposed. The robot hand can be freely configured with different number and configuration of modular fingers according to the work needs. Driving motion is achieved by the rigid structure of the screw and the connecting rod. A finger-connecting mechanism is designed on the palm of the robot hand to meet the needs of modular finger’s installation, drive, rotation, and sensor connections. The fingertips are made of hollow rubber to enhance the stability of grasping. Details about the design of the robot hand and analysis of the robot kinematics and grasping process are described. Last, a prototype is developed, and a grab test is carried out. Experimental results demonstrate that the structure of proposed modular robot hand is reasonable, which enables the adaptability and flexibility of the modular robot hand to meet the requirements of various grasping modes in practice

A New Generation of Magnetorheological Vehicle Suspension System With Tunable Stiffness and Damping Characteristics

As the concept of variable stiffness (VS) and variable damping (VD) has increasingly drawn attention because of its superiority on reducing unwanted vibrations, dampers with property of varying stiffness and damping have been an attractive method to further improve vehicle performance and driver comfort. This paper presents the design, prototyping, modeling, and experimental evaluation of a VS and VD magnetorheological (MR) vehicle suspension system. It was first characterized by an INSTRON machine. Then, a phenomenological model was proposed to capture the characteristics of the damper and TS fuzzy approach was used to model the quarter car system where the proposed damper was installed. Different controllers, including skyhook, short-time Fourier transform and state observer based controller were designed to control the damper. Experimental results demonstrate that the quarter car system with the VS and VD suspension performs best in terms of reducing the sprung mass accelerations comparing with other suspensions

Advanced vehicle suspension with variable stiffness and damping MR damper

Researchers are always looking for ways to improve vehicle comfort and the idea of using variable stiffness and damping suspension systems has been attracting attentions. The presented research has designed, fabricated, and tested an innovative magnetorheological damper which is capable of controlling both stiffness and damping. This paper presented the detailed design and working principle of the advanced damper first and then detailed how the prototyped damper was tested by an MTS machine. The testing results verified its stiffness and damping controllable capability. Then a quarter-car model with the advanced damper was built to evaluate the performance of the damper. Sliding mode control was used to control the damper and the simulation results verified the variable stiffness and damping damper performs the best on vibration control compared with other dampers

Effects of Grafting Degree on the Physicochemical Properties of Egg White Protein-Sodium Carboxymethylcellulose Conjugates and Their Aerogels

To improve the mechanical strength and oil-loading performances of egg white protein (EWP) aerogel, the effects of different grafting degrees on the modification of EWP by sodium carboxymethylcellulose (CMC-Na) were investigated. After different dry-heat treatment durations (0, 12, 24, 36, and 48 h), the EWP/CMC-Na conjugates with different grafting degrees (noted as EC0, EC12, EC24, EC36, and EC48, respectively) were obtained. Subsequently, the physicochemical properties of the conjugates, as well as the microstructure, mechanical properties, pore parameters, emulsification properties and oil-carrying properties of the conjugated aerogels, were characterized. The results showed that EC12 (with a grafting degree of 8.35%) aerogel possessed a uniform structure, the largest specific surface area, and the best emulsification performance. This facilitated a more robust aerogel (2.05 MPa) with nearly three times the mechanical strength of EWP aerogel. Moreover, this had a positive influence on the efficient loading and stable retention of oil. EC12 aerogel thus achieved an oil absorption capacity of 5.46 g/g aerogel and an oil holding capacity of 31.95%, and both values were nearly 1.7 times higher than those of EWP aerogel. In general, the EWP-based aerogel with a grafting degree of 8.35% had the best mechanical and oil-loading properties

Viscoelastic properties of gallium-indium alloy

The viscoelastic properties of a gallium-indium alloy in the pre-yield region make it easier to understand their characteristics, particularly the varying degrees of stiffness and damping properties. These viscoelastic properties were measured with a straincontrolled rheometer, where both strain amplitude sweep mode and the angular frequency sweep mode were conducted. Three groups of experiments were carried out in the strain amplitude sweep mode. In the angular frequency sweep mode, the storage modulus G\u27 and the loss modulus G\u27\u27were investigated at the linear region, the critical region, and the non-linear region. Experimental results indicate that the gallium-indium alloy exhibited similar viscoelastic properties. The linear viscoelastic region takes place when the strain amplitude is less than the critical strain amplitude of 1%. At the critical regime, the gallium-indium alloy has the strongest relative elasticity. These results are helpful to understand the intrinsic properties of gallium-indium alloys and find their application in flexible circuits, soft robotics, self-healing, and mechanical shock absorption

Understanding the Role of Shallow Groundwater in Improving Field Water Productivity in Arid Areas

Soil water and salt transport in soil profiles and capillary rise from shallow groundwater are significant seasonal responses that help determine irrigation schedules and agricultural development in arid areas. In this study the Agricultural Water Productivity Model for Shallow Groundwater (AWPM-SG) was modified by adding a soil salinity simulation to precisely describe the soil water and salt cycle, calculating capillary fluxes from shallow groundwater using readily available data, and simulating the effect of soil salinity on crop growth. The model combines an analytical solution of upward flux from groundwater using the Environmental Policy Integrated Climate (EPIC) crop growth model. The modified AWPM-SG was calibrated and validated with a maize field experiment run in 2016 in which predicted soil moisture, soil salinity, groundwater depth, and leaf area index were in agreement with the observations. To investigate the response of the model, various scenarios with varying groundwater depth and groundwater salinity were run. The inhibition of groundwater salinity on crop yield was slightly less than that on crop water use, while the water consumption of maize with a groundwater depth of 1 m is 3% less than that of 2 m, and the yield of maize with groundwater depth of 1 m is only 1% less than that of 2 m, under the groundwater salinity of 2.0 g/L. At the same groundwater depth, the higher the salinity, the greater the corn water productivity, and the smaller the corn irrigation water productivity. Consequently, using modified AWPM-SG in irrigation scheduling will be beneficial to save more water in areas with shallow groundwater

Takagi-Sugeno fuzzy control for semi-active vehicle suspension with a magnetorheological damper and experimental validation

Much research has gone into developing advanced control algorithms for semi-active suspension. Experimental validation of these control algorithms is critical for their practical applications. This paper investigates a state-observer-based Takagi-Sugeno fuzzy controller (SOTSFC) design for a semi-active quarter-car suspension installed with a magnetorheological (MR) damper and provides proof of the effectiveness of the proposed controller. To conduct the test, a quarter-car test rig and control system hardware were used. Then, a new MR damper was designed and built to fit with the test rig. After that, the SOTSFC for the quarter-car test rig was developed. Finally, several tests were conducted on the quarter-car suspension in order to investigate the real effect of the SOTSFC. It was then compared with the use of a skyhook controller to demonstrate its benefits

Takagi–Sugeno Fuzzy Control for Semi-Active Vehicle Suspension With a Magnetorheological Damper and Experimental Validation

Much research has gone into developing advanced control algorithms for semi-active suspension. Experimental validation of these control algorithms is critical for their practical applications. This paper investigates a state-observer-based Takagi-Sugeno fuzzy controller (SOTSFC) design for a semi-active quarter-car suspension installed with a magnetorheological (MR) damper and provides proof of the effectiveness of the proposed controller. To conduct the test, a quarter-car test rig and control system hardware were used. Then, a new MR damper was designed and built to fit with the test rig. After that, the SOTSFC for the quarter-car test rig was developed. Finally, several tests were conducted on the quarter-car suspension in order to investigate the real effect of the SOTSFC. It was then compared with the use of a skyhook controller to demonstrate its benefits

Broadband nonlinear behaviour of a soft magneto-sensitive elastomer cantilever under low-frequency and low-magnitude excitation

In this article, a soft magneto-sensitive elastomer cantilever with strong nonlinear behaviour is presented. With the help of a permanent magnet, a strong nonlinear behaviour is observed under low-frequency and low-magnitude excitation, which demonstrated its potential for vibrational energy harvesting. A theoretical model is developed which incorporates the nonlinear magnetic interaction in an Euler-Bernoulli beam. The theoretical model is further discretized using finite element method, and the frequency response was obtained through numerical simulation. Frequency sweep experiment was conducted to validate the model and investigate the nonlinear behaviour of the cantilever under different excitations. With the validated model, various contributing factors were parametrically studied to investigate their influences towards the dynamic behaviour of the cantilever. The results show that magnetic force dominates the linear stiffness increase of soft magneto-sensitive elastomer cantilever rather than the magnetorheological effect, and the nonlinear performance of soft magneto-sensitive elastomer cantilever mainly derives from horizontal magnetic force variations during vibration. These properties make the soft magneto-sensitive elastomer cantilever an attractive candidate to automatically tune and broaden the operational bandwidth of vibrational energy harvesters