A smart material based approach to morphing

This presentation gives an overview of the Shape Memory Alloy (SMA) based approach to the research and13; development of adaptive/smart/morphing airframe structural technologies at the Advanced Composites13; Division, NAL. Central to this approach is the efficient integration of thermal NiTi SMA elements with13; polymeric carbon composites. The SMA elements could be either externally placed or embedded in the13; polymeric composite. The external connection could be in the form of mechanisms / devices

Ethernet based online process monitoring and controlling of a plant having RS-232 or RS-485 equipment

The most popular and traditional communication link among the plant equipment is either RS-232 or RS-485. Generally, these links are extended to a plant computer for Supervisory Control And Data Acquisition (SCADA) purpose. There are many benefits in upgrading such a system into an Ethernet enabled system (Reference 1). One can not only increase the number of devices that can be interfaced to a single computer, but also access the plant devices from multiple computers that are geographically distributed. The plant computer’s bus structures, such as ISA or PCI, and the availability of RS- 232 or USB ports will not be a constraint in increasing the number of serial port devices, once they are Ethernet enabled. A common method for Ethernet enabling is to replace the existing RS-232 / RS-485 equipment with those having built-in Ethernet. This is an expensive and time-consuming solution. A compromised solution will be to connect the plant computer to the LAN (Local Area Network). This method can help in the remote viewing of the plant data but online monitoring and controlling will not be possible. Further, if the plant computer fails, the remote monitoring will not be possible. A better technique in terms of cost, time-to-implement, redundancy and reliability will be to use a multi-channel Serial Device Server (SDS). The SDS accepts number of RS- 232/RS- 485 based devices and provides one Ethernet port through which they all can be accessed

Open Source Embedded Controller for SMA actuated Morphing Wing MAV

Micro Air Vehicle (MAV) is a lightweight flying object of around 300mm size that can be flown by a ground pilot through radio commands or through an autopilot built on an embedded system. Appropriate morphing or shape changing of MAV wing during flight has the potential to give different aerodynamic benefits, similar to birds but the implementation of such a system poses weight, power, response time and size challenges. The all-up weight of MAV should be around 300g and the flight is powered by a on-board battery which has very less power to spare, given the difficulty to meet the target endurance of about 30 minutes. Active morphing was achieved by drooping the Leading Edge (LE) of MAV wing. Such a morphing form has the potential to give higher lift during takeoff, low speed loitering, negotiation of high-rise structures and landing. A MAV designed and developed at NAL, namely 'Black Kite' was used for this purpose. This paper presents the Open source embedded controller namely Arduino adapted for the morphing of MAV using multiple Shape Memory Alloy based actuators. It describes a form of wing morphing obtained by drooping the leading edge, design and development of SMA based actuators, measurement and control of degree of morphing, integration of the whole system using the arduino autopilot board and the flight testing

Hot bonded repair of aircraft structures

Ever since Boeing 707 passenger jet flew in 1950 with 2% of composites in its airframe, the use of composite structures is steadily increasing in military, civil and unmanned aircraft. Extensive use of composites structures, amounting to 45% of airframe weight in LCA and 50% in Boeing's dreamliner-787 are testimonies to this. While composites brought in several advantages, such as weight and cost reduction, fuel saving and improvised design solutions, they also posed new challenges in terms of maintenance and repair related issues. Unlike metallic structures, composites need special equipment for repair. Once the repair schemes/techniques are properly established, composites became the most preferred choice even for the repair of metallic structures. Repair techniques play an important role in increasing the useful life of aircraft structures. They increase the confidence level of the user and promote the usage of composites. Several structural repair techniques are being evolved to enhance the aircraft service life. Among these repair techniques, hot bonding is widely acclaimed for its ability to restore strength to reasonable levels, amenability for in-situ or field repair and suitability for both metallic and composite structures. This talk provides an insight into the nuances of hot bonded repair. It describes the practical problems associated with the in-situ repair of aircraft structures, such as the temperature gradient, quality control, flush repair of structures with one side access etc. The issue of temperature gradient during polymer cure that occurs due to non-uniform thickness, partial heating, variation in constituent materials etc., is explained. As a solution to the temperature gradient problem, the Multi-zone hot bonder, developed by the author is presented in detail. The additional benefits of the multi-zone hot bonder, which include curing a travel coupon (for destructive testing) along with the repair and performing simultaneous repair at multiple locations are highlighted. A special case of flush repair of structures constrained by one side access, using Shape Memory Alloys is also presented

Development of a computer based process control system for an autoclave to cure polymer matrix composites

Autoclave is a process control system used in a number of industries such as aerospace, pharmaceutical, chemical, food processing and health care. NAL has pioneered the design and development of autoclaves in India to cure polymer matrix composites. This paper explains the development of a computer based multi-mode process control system for an autoclave, which is used to fabricate composites structures for aircrafts, satellites and other aerospace applications. This system comprises of a desktop computer, Programmable Logic Controller (PLC), analog data scanner, PID based Front-End Controllers (FEC) etc. It provides Auto, Semi-auto and Manual modes of operation. This paper also presents the strategies for control of autoclave temperature, part temperature and autoclave pressure along with the computer integration aspects. These techniques have been realized and successfully implemented in a couple of autoclaves

An improved technique and its implementation for control of high power heaters in large autoclaves and similar plants

This paper presents an improved technique and its implementation for control of high power heaters in large autoclaves and similar plants. These plants are equipped with electrical heaters, which are grouped into number of banks to reduce the quantum of load/power change and improve operability, controllability and reliability. Conventionally, each heater bank is controlled through a power controller (usually Silicon Controlled Rectifier based). The total number of power controllers employed in a system will be equal to the total number of heater banks and they all share a common control signal provided by the temperature controller. While this is an obvious method, it is very expensive and results in decreased power factor and increased harmonic distortions. To overcome the above limitations, this paper explains a better technique; namely, ‘Heater Power Steering Logic (HPSL)’ and its implementation using Analog circuit and also using Programmable Logic Controller

In-flight control of MAV wing camber using Shape Memory Alloy Actuators and flex sensor

Objective/Aim: A morphing system that can dynamically change the camber or shape of Micro Air Vehicle wing provides specific aerodynamic benefits by increasing the lift coefficient. Though many research papers have reported the benefits of morphing, there are hardly any reports on morphing of MAV during flight. The challenge is to measure, effect and control the deflection angle of the wing within the constraints of space (few square centimeter), power (< 5W) and weight (< 8g) in MAV. This paper presents a flex sensor and Shape Memory Alloy (SMA) based in-flight wing deflection measurement and control system. A novel method of transmission of deflection angle and SMA parameters along with other flight data to the Ground Control Station (GCS) and their transfer to MATLAB for online analysis is also presented. Methods and materials: Fixed wing MAV, namely 'black kite' was chosen for the morphing trials. Morphing involved change of camber through drooping of wing Leading Edges (LE) along the plane's lateral axis. A flex sensor bonded to the wing, changes its resistance as a function of wing deflection. This was read as a voltage signal in the Ardu-ino flight controller. To overcome the inaccuracy of flex sensor, software-based auto nulling and averaging were implemented as a sub-function of auto pilot code. The actuator requirements for morphing were experimentally determined and a NiTinol SMA wire of appropriate dimension was chosen. SMA actuator generates force and displacement due to temperature induced phase transformation, which can be controlled by varying the magnitude and duration of SMA current. This was realized by Pulse Width Modulation of SMA current through a MOSFET. A PID algorithm with integral reset implemented on the Ardu-ino controller, computes the required pulse width based on the error between actual and set deflection angles (commanded by the ground pilot or the auto pilot). Using a Zigbee transceiver pair and by modifying the auto pilot and GCS codes (open source) the deflection angle and SMA parameters were transmitted, extracted and fed to MATLAB for online trending and other analysis

Advanced hot bonding system for repair of Aerospace Structures

Repair techniques play an important role in increasing the useful life of the aerospace structures. They increase the confidence level of the user and promote the application of composites. Among the various repair techniques, hot bonding is widely acclaimed for its ability to restore the strength close to the original values. It is used for the repair of metal or composites structures. Hot bonding performed using flexible heater blanket and vacuum bag is the most suitable method for in-situ repair. Hot bonding is performed through elevated temperature cured adhesive system, which increases the glass transition temperature and hence the service temperature of the final product. These adhesive systems are sensitive to temperature gradient. If the gradient exceeds ±5oC, the cross-linking process and the quality of repair is adversely affected. In the hot bonding process, only the repair area is heated and the rest of the part is left in atmospheric condition. Due to partial heating, the region below the centre of the heater gets hotter than the surrounding. This problem worsens if the job has skin and spar construction or has non-uniform cross-section as in the case of aircraft control surfaces or windmill blades. The hot bonding equipment currently being imported (none manufactured within India) does not ensure temperature uniformity. This paper discusses the design and development aspects of multi-zone, portable hot bonding equipment, which overcome the above problems. Multiple numbers of appropriately placed heater blankets, sensors and a data acquisition device coupled with a novel control algorithm and multi-threaded software has resulted in the portable and reliable hot bonder. The equipment was tested on typical aircraft parts, such as an aluminium rudder and a composites fin tip. The conventional single heater blanket method has resulted in a temperature gradient of over 12oC, while this product has limited the temperature gradient to within ±1.5oC

Design and development of Control and Instrumentation system for Aerospace class autoclave.

Autoclave has enabled the replacement of metallic aerospace structures by advanced composites structures. It is a batch process control system that provides controlled temperature, pressure and vacuum environment for accurate and consistent processing of polymeric composites. Extensive use of composites in Boeing 787 Dreamliner aircraft is a testimony to the advancements in polymeric composites and their reliable processing in autoclaves. Advanced composite materials are very expensive and often require many man months of preparatory work before they are loaded into autoclave for processing also known as curing. The polymer cure process is irreversible and deviation in process parameters beyond the narrow tolerance levels would result in the rejection of composites. Hence the autoclave in general and Control and Instrumentation system in particular should have adequate redundancy, fail-safe design, fault tolerance and high reliability. This paper presents the conceptualization, design, development, integration and commissioning of open architecture, multimode autoclave C&I system including the associated electrical and software systems