Parameter Identification of the Suspended Load Backpack due to Human Gait for outdoor activities for Minimization Musculoskeletal Load
Backpack is considered to be the most convenient carrier to carry an extra load. In military and rescue team, backpack is often used to carry supplies, communication devices, and other equipments that often the load can be heavier than the ergonomic standard. When the backpack is used in difficult terrains, using backpack itself may lead to some muscle injuries due to the large amount of load to carry. Muscle injuries may be arising due to the impact force during user running or jumping. To reduce the effect of impact force in conventional backpack, shoulder straps and hip attachments should be designed to provide an in‐phase movement between the load and the trunk. Theoretically, the effect of impact force may be significant reduce if out‐of‐ phase movement between the load and the trunk could be occurring. Suspended‐load backpacks have been proposed as a way to allow the backpack load vertical movement relative to the back position and minimize the amplitude of backpack load that caused the ground reaction force during user running. However, Significance of altering ground reaction force pattern was related with the backpack suspension parameters and also running parameters. Since the running speed is related with frequency pattern of ground reaction force, a natural frequency of backpack suspension based on the linier spring configuration was depending of a load weight. The paper was described the alternative configuration that promising a natural frequency of backpack suspension was in‐sensitive with a load weight. In order to improving the user’s comfort and find the effective parameter of the backpack suspension, we proposed novel procedure to estimate dynamic characteristic of suspended‐load backpack system based on modeling and empirical procedure. On modeling procedure, the dynamic parameter of system was indentified based on impulse response of backpack suspension. Based on obtained model, a simulation was done to predict dynamic characteristic of system. Validation of obtained model was tested using the vertical harmonic movement of human gait motion analysis. Finally, the degree of out‐of‐ phase movement between the load and the trunk as function a running speed and backpack load was also simulated using obtained model of suspended backpack with various stiffness setting.
The results show that the simple simulation and modeling of dynamic characteristic of suspended‐load backpack system could be used to determine the affectivities of its system. With an appropriate approximation, the physical characteristic of the system could be found with a transfer function as representation from that system. The simulation is valid enough to represents the real system of suspended‐load backpack. The corre‐lation of load variation and walking speed to the system re‐sponse could be determined as a function of its natural frequency. In order to make an improvement of the backpack design, the simulation shows that the natural frequency of the system is a function of mass and spring coefficient, and less natural frequency, the system response could have a better performance in reduction the ground reaction force. From the relation of mass and spring coefficient known that to reach better suspension system, the spring coefficient must directly proportional to the load mass, heavier load mass which used in the backpack, the spring coefficient value must be bigger than if lighter load mass is used in the system.
This research proved that the inspection of dynamical system could be determined with a simple and cheaper way with satisfying results, so these simulation methods could be applied in the real design process to improve the backpack performance.
LIST OF RESEARCH OUTPUT
• Narendra Kurnia Putra, Suprijanto and Andar Bagus Sriwarno, ”Dynamic Modeling and Simulation of the Suspended-Load Backpack to Obtain Optimal Suspension Parameters and Reducing Effect of Ground Reaction Force”, 6th World Congress of Biomechanics (WCB 2010). August 1-6, 2010 Singapore IFMBE Proceedings, 2010, Volume 31, Part 1, 111-114, DOI: 10.1007/978-3-642-14515-5_29, (http://www.springerlink.com/content/v14jv384m6k83106/)
• Suprijanto, Narendra Kurnia Putra and Andar Bagus Swiwarno, ” Novel Procedure to Estimate Dynamic Characteristic of Suspended-Load Backpack System Based on Empirical and Modeling Procedure”, submitted to journal
• New Prototype Suspended Backpack
Figure (a) First Version of Prototype Suspended Backpack using single slider in the center of frame (b) New Prototype Suspended Backpack using double slider in the left and right frame
HEAD OF RESEARCH TEAM: Dr. Suprijanto ST MT
TEAM MEMBERS: Andar Bagus Sriwarno, M.Sn. Ph.D.
OFFICIAL ADDRESS: Medical Instrumentation Laboratory‐Instrumentation and Control Research Group and Ergonomic Desain Studio, Human and Industrial Product Research Group