Nonlinear Energy Harvesting Device For Low Frequency Human Motion Application

Energy harvesting from ambient sources had received much attention in the past few years due to worldwide awareness on green technology expands. In vibration based energy harvesting, resonant linear generator are commonly used as the harvesting devices. However, a linear generator induces several limitations. The power harvested by a linear generator is proportional to the cube of excitation frequency and the power is maximum in a narrow bandwidth only. In this research, human motion vibration was selected as an input excitation and its frequency content is investigated. The frequency of human motion was investigated by placing a vibration recorder on a test subject under 5km/h walking and 9 km/h jogging speed.The investigation shows that the human motion vibration is distributed in the low frequency region. Hence, a device that can operate optimally with low frequency input and has the ability to overcome the narrow bandwidth limitation is designed. A device is designed to overcome the limitations of the linear generators. This device has the combination of the tuning, frequency-up conversion, multimodal and non-linear techniques. The aim is to amplify the input frequency to a higher frequency and at the same time, widen the bandwidth of response. The frequency-up mechanism is made by transforming the translation motion into the rotary motion by using gear ratio to amplify the response to a higher rotational speed. Winding springs are used with twistable enclosure cap to alter the device stiffness. The angles of twist of the enclosure cap are ranging from 180 degree to 900 degree. Two oscillating masses are connected to the device. Each mass can be set with different characteristic to widen the bandwidth. The two masses are also configured with non-linear softening and non-linear hardening properties to further widen the bandwidth. The non-linearities of the system are changed by varying the magnets gap. The non-linear restoring force of the system shows the influences of the linear coefficient and non-linear coefficient. The device is then investigated with two sets of experiments. The quasi-static measurement is to investigate the system stiffness and dynamic measurement is to investigate its response across a frequency range. In the dynamic measurement the device is excited with sinusoidal inputs and real human motion inputs. Overall, the results obtained from the experiment show that device is able to produce frequency amplification. The response also shows that with a properly tuned system, both softening and hardening can produce a flat response which is insensitive to excitation frequency as well as at amplified amplitude

A Combined Softening and Hardening Mechanism for Low Frequency Human Motion Energy Harvesting Application

This paper concerns the mechanism for harvesting energy from human body motion. The vibration signal from human body motion during walking and jogging was first measured using 3-axes vibration recorder placed at various places on the human body. The measured signal was then processed using Fourier series to investigate its frequency content. A mechanism was proposed to harvest the energy from the low frequency-low amplitude human motion. This mechanism consists of the combined nonlinear hardening and softening mechanism which was aimed at widening the bandwidth as well as amplifying the low human motion frequency. This was realized by using a translation-to-rotary mechanism which converts the translation motion of the human motion into the rotational motion. The nonlinearity in the system was realized by introducing a winding spring stiffness and the magnetic stiffness. Quasi-static and dynamic measurement were conducted to investigate the performance of the mechanism. The results show that, with the right degree of nonlinearity, the two modes can be combined together to produce a wide at response. For the frequency amplification, the mechanism manages to increase the frequency by around 8 times in terms of rotational speed

Heavy Military Land Vehicle Mass Properties Estimation Using Hoisting and Pendulum Motion Method

Mass properties such as the centre of gravity location, moments of inertia, and total mass are of great importance for vehicle stability studies and deployment. Certain parameters are required when these vehicles need to be arranged inside an aircraft for the carrier to achieve proper mass balance and stability during a flight. These parameters are also important for the design and modelling process of vehicle rollover crash studies. In this study, the mass properties of a military armoured vehicle were estimated using hoisting and pendulum method. The gross total weight, longitudinal and vertical measurements were recorded by lifting the vehicle using a mobile crane and the data were used to estimate the centre of gravity. The frequency of vehicle oscillation was measured by applying swing motion with a small angle of the vehicle as it is suspended on air. The centre of gravity and mass moment of inertia were calculated using the vector mechanics approach. The outcomes and limitations of the approach as discussed in details

Design Of Formula Varsity Race Car Suspension Upright

This paper presents the design of a suspension upright for Formula Varsity race car. CATIA V5 R16 CAD software was utilized to generate the 3D model of the final upright design. Aluminum alloy grade 6061-T6 was selected for the upright construction material due to its low density and good mechanical strength as well as wide availability in different sizes. Structural analysis using finite element method (FEM) was implemented to analyze the structural strength. CATIA V5 Generative Structural Analysis workbench as used in the analysis. Results from the structural analysis shows that the upright design has a factor of safety of 12.1, which theoretically proved that the structure is able to perform safely as per design requirement. A part from that, through utilization of aluminum alloy as the upright material, the weight of the component is able to reduce up to 57.5% compared to the upright used in 2010 UTeM Formula Varsity race car. Thus, the new upright design is able to provide the crucial weight saving needed for an efficient race car without compromising its structural strength and safety

Translational-rotary frequency up conversion vibration based energy harvesting device for human body motion

This paper presents some preliminary studies on the frequency-up conversion method for low frequency application energy harvesting device, mainly from human body motion, by employing the translational-rotary mechanism. Vibration signals from different parts of the human body were first measured when the human subject was walking at 5 km/h and jogging at 9 km/h. The signals obtain from the test was then reconstructed using Fourier Transform and it was found that frequency content of human body motion was in the range of 1 Hz – 25 Hz.. A preliminary experiment was conducted to check on the ability of the mechanism to amplify the excitation frequency. Although the experiment was not optimized, the device was able to amplify input frequency up to 3.6 times

Translational-rotary frequency up conversion vibration based energy harvesting device for human body motion

This paper presents some preliminary studies on the frequency-up conversion method for low frequency application energy harvesting device, mainly from human body motion, by employing the translational-rotary mechanism. Vibration signals from different parts of the human body were first measured when the human subject was walking at 5 km/h and jogging at 9 km/h. The signals obtain from the test was then reconstructed using Fourier Transform and it was found that frequency content of human body motion was in the range of 1 Hz – 25 Hz.. A preliminary experiment was conducted to check on the ability of the mechanism to amplify the excitation frequency. Although the experiment was not optimized, the device was able to amplify input frequency up to 3.6 times

How many roads must a Malaysian walk down? Mapping the accessibility of radiotherapy facilities in Malaysia.

BackgroundThe accessibility to radiotherapy facilities may affect the willingness to undergo treatment. We sought to quantify the distance and travel time of Malaysian population to the closest radiotherapy centre and to estimate the megavoltage unit (MV)/million population based on the regions.Materials & methodsData for subdistricts in Malaysia and radiotherapy services were extracted from Department of Statistics Malaysia and Directory of Radiotherapy Centres (DIRAC). Data from DIRAC were validated by direct communication with centres. Locations of radiotherapy centres, distance and travel time to the nearest radiotherapy were estimated using web mapping service, Google Map.ResultsThe average distance and travel time from Malaysian population to the closest radiotherapy centre were 82.5km and 83.4mins, respectively. The average distance and travel were not homogenous; East Malaysia (228.1km, 236.1mins), Central (14.4km, 20.1mins), East Coast (124.2km, 108.8mins), Northern (42.9km, 42.8mins) and Southern (36.0km, 39.8mins). The MV/million population for the country is 2.47, East Malaysia (1.76), Central (4.19), East Coast (0.54), Northern (2.40), Southern (2.36). About 25% of the population needs to travel >100 km to get to the closest radiotherapy facility.ConclusionOn average, Malaysians need to travel far and long to reach radiotherapy facilities. The accessibility to radiotherapy facilities is not equitable. The disparity may be reduced by adding centres in East Malaysia and the East Coast