Electric buses undergo frequent start-stop cycles. Their batteries are frequently required to supply high discharge currents during acceleration and sink high charging currents during regenerative braking.

However, frequent charging and discharging cycles cause degradation of battery life. The batteries may need to be replaced atleast once during the lifespan of the electric bus.

Batteries are usually oversized in order to meet the power demand in addition to meeting the range requirement. This increases their weight, volume and cost.

The battery life could be significantly improved by using ultracapacitors in combination with batteries.

Selection and optimization of battery and ultracapacitor sizes, powertrain and hybrid energy storage configuration and the power split control strategy are the key challenges being addressed.

Electric propulsion for aircraft can significantly improve aircraft efficiency and reduce in-flight emissions.

However, the specific energy of currently available batteries is about 60 times lesser than that of aviation fuel. Therefore, the range of battery powered aircraft will be significantly lesser than that of the conventional aircraft.

A methodology to examine the feasibility of electric propulsion for an aircraft was developed.

The feasibility of electric propulsion for a Medium Altitude Long Endurance (MALE) Unmanned Aerial Vehicle (UAV) is examined for battery specific energy trends ranging from the state-of-the-art projected up to the year 2035.

The feasibility is assessed from the standpoint of level flight at typical operating speeds and altitudes.

The lift and drag forces are estimated from typical equations for subsonic flight, and the dynamic equilibrium and energy balance equations are solved.

The wing area required to produce adequate lift to balance the weight of the UAV is compared to the available area and the wing loading as compared to that of the maximum takeoff mass of the baseline conventional UAV.

A model of the powertrain of a sub one ton payload mini-truck converted into a post-transmission parallel hybrid electric vehicle by retrofitting a planetary gear transmission was developed using MATLAB/Simulink.

This vehicle can be operated in two types of hybrid modes, namely, speed coupling and torque coupling.

The aim of this work was to optimize the transmission design and the control strategy of the hybrid vehicle for low speed urban start-stop traffic conditions.

A simple gear shifting strategy based on upshift and downshift maps for each gear of the manual transmission is developed.

Algorithms for determining the optimum operating point of the IC engine for the required tractive torque at the wheels at a required vehicle speed for the hybrid modes were developed.

A rule-based control strategy that determines the power split between the IC engine and the electric motor was developed.

The control strategy ensures that the IC engine operates close to its optimum operating point while maintaining the battery state of charge (SOC) within the desired limits, was formulated.

Two variants of the control strategy, CS1 and CS2, were developed in order to examine the efficiency of the drivetrain in the two hybrid modes.

The conventional and hybrid powertrains were simulated over three low speed urban drive cycles having high frequencies of stops.

The SOC adjusted equivalent fuel consumption (EFC) of the hybrid drivetrain was 37-57% lower than that of the conventional drivetrain for three low speed urban drive cycles with frequent start-stop for both the control strategies.

A metric ΔSFC was introduced for obtaining the mean deviation of the IC engine’s operating point relative to the optimum over a drive cycle.

The contributions of the various modes of operation of the hybrid drivetrain and the deviation of the IC engine’s operating point were analyzed for the three drive cycles.

The performance of the control strategy CS2 were found to be better than that of CS1 for all the three drive cycles.

A comparative analysis of the two hybrid modes showed that the torque coupling hybrid mode provided significantly better improvement in EFC and exhibits lower values of ΔSFC than speed coupling for all the three drive cycles. EFC of the hybrid vehicle was 15-26% lesser than that of conventional for various urban drive cycles.

The analysis of the effect of variation of the initial SOC on the performance of the hybrid drivetrain showed that the best improvement in the EFC and the least values of ΔSFC values were obtained for the initial SOC in the range of 50-70%.

The effect of the payload on the performance of the hybrid powertrain was examined. The improvement in EFC decreased with increase in the payload.

The transmission gear ratios, gear shifting strategy and the control strategy parameters were optimized with the objective of minimizing the EFC per unit distance covered over the three drive cycles, using a genetic algorithm.

The objective function for the optimized design was found to be marginally better than that of the hybrid drivetrain with control strategy CS2.

Research Assistantship Project-

Funded By: Tata Centre for Technology and Design, IIT Bombay

Developed a prototype of a semi-autonomous human–electric hybrid tricycle in a team of five.

Worked in a team of 4 for integration of electrical and mechanical systems and vehicle road testing.

Achieved cruise control upto 10 km/h with a bicycle and the tricycle as leader-follower.

Co-ordinated vehicle design, material procurement and fabrication in a team of 5.

Mentored a team of 7 for design and fabrication of the second prototype of the hybrid electric tricycle

Gained proficiency in bicycle mechanics and metal fabrication using hand tools and machine tools

Link to Project Webpage

Proposed a novel approach of modelling the material properties of thin rectangular perforated plates with square and triangular perforation pattern using Heaviside step functions

Estimated the fundamental frequency of transverse vibrations of plates for boundary conditions: all edges simply supported and fully clamped using Rayleigh’s method using Maple

Analytical results within 90% accuracy relative to that of modal analysis using ANSYS.

Designed and fabricated 5 specimens of perforated plates and the fixture for experimental modal analysis.