Ravi Kant Jain

SCARA based peg-in-hole assembly using compliant IPMC micro gripper

Robotic assembly is difficult as there always exist position errors between two mating parts. Compliance is added in a selective compliant assembly robot arm (SCARA) in the form of a two ionic polymer metal composite (IPMC) fingers based micro gripper. This micro gripper is integrated at the end effector position of a SCARA robot. Peg-hole interaction is analytically modeled and based on it the force required to correct the lateral and angular errors by IPMC is calculated. A proportional-derivative (PD) controller is designed to actuate the IPMC to get the desired force for correcting the peg position before assembly. Simulations and experiments were carried out by developing an IPMC micro gripper and using it to analyze various cases of peg in hole assembly. The experimental results prove that adding compliance through IPMC helps in peg-in-hole assembly.

Two IPMC Fingers Based Micro Gripper For Handling

This paper presents the behavior of two finger based micro gripper which is made of Ionic Polymer Metal Composite (IPMC), an Electro Active Polymer (EAP). An IPMC shows great potential as high-displacement and light weight actuator. Low mass force generation capability is utilized for micro gripping in micro assembly. IPMC responds to low voltage in the range of 0-3V. The material contains an electrolyte which transport ions in response to an external electric field. IPMC actuation for micro gripping is produced by deflecting material according to bending moment theory. An external electric field generated by suitable RC circuit causes this deflection. It is found that an IPMC actuates from 1–5 seconds. The maximum jaw opening and closing position of micro gripper are found to be 5 mm and 0.5 mm respectively. The effect of tempearture, as observed, shows that the acceptable limit varies from 23.1°C to 30.4°C while an IPMC is in operation. An experimental proto type is developed for evaluation of performance.

Development of sulfonated poly(vinyl alcohol)/polpyrrole based ionic polymer metal composite (IPMC) actuator and its characterization

In the present study, a novel sulfonated poly(vinyl alcohol)/polypyrrole polymer membrane sandwiched between platinum (SPVA-Py-Pt) is fabricated for a bending actuator which can be used in microrobotic applications. To examine the suitability of SPVA-Py-Pt based ionic polymer metal composite (IPMC) for microrobotic applications, ion exchange capacity (IEC), water uptake, proton conductivity, water loss, cyclic voltammetry (CV), linear sweep voltammetry (LSV), Fourier transform infrared spectroscopy (FTIR), thermal stability, and tip displacement studies are performed. The water holding capacity of the IPMC membrane is found to be 82.23% at room temperature for 8 h of immersion time. The IEC and proton conductivity of the IPMC membrane is found to be 1.2 meq g−1 and 1.6 × 10−3 S cm−1, respectively. Maximum water loss from IPMC is achieved as 31% at 5 V for a time period of 16 min. Based on electromechanical characterization, the maximum tip displacement of SPVA-Py-Pt IPMC (size 30 mm length, 10 mm width, 0.08 mm thickness) is 18.5 mm at 5.25 V. The major advantages of this new type of IPMC are good film-forming capability, short processing time, low cost of fabrication, good flexibility, high thermo-mechanical stabilities, good ion exchange and water holding capacities and proton conductivity as compared to other types of IPMC actuators. The comparison with other type of IPMC actuators is also summarized. A multi SPVA-Py-Pt IPMC based micro-gripping system is developed that shows the potential of microrobotic applications.

Microassembly by an IPMC-based flexible 4-bar mechanism

A new design for a flexible 4-bar mechanism using ionic polymer metal composite (IPMC) for micropeg-in-hole assembly is proposed. In such assembly a peg is inserted into a hole by a flexible 4-bar mechanism. During assembly there exist both lateral and angular errors in the positioning of the peg. Due to this misalignment, the forces at the contact point between the peg and hole cause a change in the coupler path. In order to accommodate these forces, an IPMC-based microgripper is fitted at the center of the coupler in the flexible 4-bar and an IPMC patch is also attached on the coupler. The IPMC patch, when actuated, applies a moment on the coupler, thus changing its deflection. The objective of the design is to correct the deflection in the coupler path and also add compliance at the gripper during assembly. A model of the flexible 4-bar mechanism with an IPMC-based compliant gripper is made in Adams software. The simulation results show that the path of the flexible coupler can be controlled by activating the IPMC patch, while the misalignment during assembly is compensated by the IPMC microgripper. An IPMC-based flexible 4-bar mechanism was fabricated and experiments were carried out. The results prove that the path of the mechanism can be controlled and compliance can also be accommodated by the proposed mechanism during assembly.

Study and preparation of highly water-stable polyacrylonitrile–kraton–graphene composite membrane for bending actuator toward robotic application

In this article, polyacrylonitrile–kraton–graphene (PAN-KR-GR) ionomeric polymer membrane sandwiched between Pt electrode-based ionic polymer–metal composite (IPMC) actuator is developed. The aim of this study is to design and prepare multifunctional ionic polymer–metal composite membrane for robotic application. The water uptake capacity and ion exchange capacity of polyacrylonitrile–kraton–graphene ionomeric membrane is 133.33% at 45 °C for 8 h of immersion and 1.4 meq g−1 of dry membrane, respectively. Proton conductivity and maximum water loss of ionic polymer–metal composite membrane is 5.26 mS cm−1 and 38% after applying 7 V for 12 min, respectively. Scanning electron micrographs shows the smooth and uniform coating of platinum (Pt). Cyclic voltammetry, linear sweep voltammetry, Fourier transform infrared spectroscopy, thermogravimetric analysis, X-ray diffraction, and tip displacement of PAN-KR-GR-Pt IPMC membrane are also examined. A multifinger-based gripping system for dexterous handling is developed for robotic application.

Biomimetic Behavior of IPMC Using EMG Signal for Micro Robot

This paper presents the biomimetic behavior of an ionic polymer metal composite (IPMC) based artificial finger for micro robot which can be applicable in holding the object. In this work, IPMC based artificial finger is actuated by controlled electromyographic (EMG) signal. The EMG signal is taken from human index finger via EMG sensor. This signal is pre-amplified before transferring to IPMC for achieving the large bending behavior of IPMC. The biomimetic actuation behavior of IPMC is studied by movement of index finger muscles through long tendons. The stability analysis of EMG signal from human index finger is carried out by providing the proportional–integral–derivative (PID) control system. Experimentally, it is observed that IPMC finger can hold the micro component when IPMC finger is activated through EMG via human muscles and an IPMC based micro gripper is demonstrated.

Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate zirconium(IV) phosphate (PEDOT:PSS–ZrP) composite ionomeric membrane for artificial muscle applications

The PEDOT:PSS–ZrP ionomeric actuator was developed for artificial muscle applications. The polyvinyl chloride (PVC) based (PEDOT:PSS) Zr(IV) phosphate composite ionomeric membrane (PVC–PEDOT:PSS–ZrP) was successfully synthesized by a solution casting technique. Various instrumental techniques including thermogravimetric analysis/differential thermal analysis/differential thermogravimetry (TGA/DTA/DTG), energy dispersive X-ray (EDX) analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FT-IR) spectroscopy were used to characterize the PVC–PEDOT:PSS–ZrP ionomeric material. Membrane properties were evaluated in terms of ion exchange capacity, cyclic and linear sweep voltammetry, water uptake, water loss and proton conductivity. The tip displacement of the PVC–PEDOT:PSS–ZrP composite ionomeric membrane was also studied. The composite ionomeric membrane showed excellent displacement under an applied voltage. Therefore, a composite ionomeric membrane was found to be suitable for bending actuation applications in artificial muscles.

Fabrication of a silver nano powder embedded kraton polymer actuator and its characterization

A novel silver nano powder (Ag Pw) embedded kraton (KR) ionic polymer actuator was fabricated. The KR–Ag-Pw ionic polymer metal composite (IPMC) membrane was prepared by a solution casting method. The IPMC membrane shows good electro-mechanical, ion exchange, water retention (WR) and proton conductivity (PC) properties which are responsible for the high performance of the ionic polymer actuator. The physicochemical properties of the KR–Ag-Pw ionic polymer actuator were determined using X-ray diffraction, Fourier transform infra-red spectroscopy (FTIR), scanning electron microscopy (SEM) and thermogravimetric analysis (TGA) studies. After applying a voltage (0–3.5 V DC), the maximum bending behaviour is achieved up to 17 mm. By constructing a multi KR–Ag-Pw IPMC finger based gripper, it is proved that this kind of actuator has potential in robotic applications.

Multiple path generation by a flexible four-bar mechanism using ionic polymer metal composite

This article presents a novel design of a flexible four-bar crank–rocker mechanism using ionic polymer metal composite for generating multiple paths, which can be applied in microassembly. In order to control the deflection of links and the resultant path, active ionic polymer metal composite patches are fixed on the coupler and are actuated by a voltage (0–3 V direct current). The main focus of this article is to determine the number, size, and location of the ionic polymer metal composite patches to be used on the coupler to get a desired path. A dynamic model of the mechanism is made in ADAMS software and the design parameters are identified. A mathematical model of ionic polymer metal composite patch is developed through experiments to achieve the bending moment relationship with voltage, and this is used while simulating its behaviors. The simulation results show that the proposed mechanism can generate multiple paths, using different voltages for ionic polymer metal composite activation. The proposed mechanism is then fabricated, and experiments are carried out to compare the experimental and simulation results. It is proved that the proposed new mechanism is superior to earlier designs of four bars using ionic polymer metal composite, and the paths generated can more effectively be controlled.

Experimental characterizations of bimorph piezoelectric actuator for robotic assembly

Piezoelectric actuator is one of the most versatile types of smart actuators, extensively used in different industrial applications like robotics, microelectromechanical systems, micro-assembly, biological cell handling, self-assembly, and optical component handling in photonics. By applying potential to a piezoelectric actuator, it can produce micro level deflection with large force generation, very fast response, and long-term actuation as compared to other actuators. The design and analysis of the bimorph piezoelectric cantilever using proportional–integral controller are carried out where the bimorph piezoelectric actuator is used as an active actuator for providing the dexterous behavior during robotic assembly. Characterization of bimorph piezoelectric actuator carried out by controlling voltage signal provides steady-state behavior which is verified by conducting experiments. A prototype of micro gripper is also developed which shows the potential of handling small lightweight objects for robotic assembly.