We propose and develop an electrical and mechanical system model of a singleaxis linear-motion kinetic energy harvester for impulsive excitation that allows its generated load power to be numerically optimised as a function of design parameters. The device consists of an assembly of one or more spaced magnets suspended by a magnetic spring and passing through one or more coils when motion is experienced along the axis. The design parameters that can be optimised include the number of coils, the coil height, coil spacing, the number of magnets, the magnet spacing and the physical size. We use the proposed model to design optimal energy harvesters for the case of impulse-like motion like that experienced when attached to the leg of a human. We generate several optimised designs, ranked in terms of their predicted load power output. The three best designs are subsequently constructed and subjected to controlled practical evaluation while attached to the leg of a human subject. The results show that the ranking of the measured output power corresponds to the ranking predicted by the optimisation, and that the numerical model correctly Predicts the relative differences in generated power for complex motion. It is also found that all three designs far outperform a baseline design. The best energy harvesters generated an average power of 3.01mW into a 40Ω test load when driven by footsteps whose measured peak impact was approximately 2.2g. With respect to the device dimensions, this corresponds to a power density of 179.380µW/cm 3 .

Energy harvesting is employed to extend the life of battery-powereddevices, however, demanding applications such as wildlife tracking col- lars, the operating conditions impose size and weight constraints. They also only provide non-harmonic mechanical motion, which renders much of the existing literature inapplicable, which focuses on harvesting energy from harmonic mechanical sources. As a solution, we propose an energy harvesting architecture that consists of variable number of evenly-spaced magnets, forming a fixed assembly that is free to move through a se- ries of evenly-spaced coils, and is supported by a magnetic spring. We present an electromechanical model for this architecture, and evolution- ary optimization process that finds the model parameters which describe the time-domain behaviour observed in ground truth measurements. The resulting model can predict the time-domain behaviour of the energy har- vester for any configuration of the proposed architecture and for any me- chanical excitation. We also propose an optimization process that, using the electromechanical model, optimizes the energy harvester configuration to maximize the power delivered to a resistive load. The resulting opti- mized harvester design is specific to the particular kind of non-harmonic mechanical excitation to which it will be exposed. To demonstrate the effectiveness of our proposed model and optimization procedure, we con- structed four energy harvesters, each with different configurations, and compared their measured behaviour with that predicted by the model, given an excitation that approximates footstep-like motion. We show that the model predictions were consistently within 25% of the RMS load volt- age. We then synthesize an optimal energy harvester using the proposed optimization process. The resulting optimal design was constructed and tested using the same footstep-like excitation, and delivered an average power of 1.526mW to a 30Ω load. This is a 2.8-fold improvement over an unoptimized reference design. We conclude that our proposed behaviouralmodel and optimization process allows the determination of energy har- vester designs that are optimized for a non-harmonic and specific input excitatio