A NOVEL GAIT-INSPIRED FOUR-BAR LOWER LIMB EXOSKELETON TO GUIDE THE WALKING MOVEMENT

Background: Walking is a complex process that involves rhythmic movement of lower limb along with the coordination of brain, nerves and muscles. If the coordination is disturbed, gait may be effected or disordered. Therefore, it should be treated effectively and efficiently using assistive devices/exoskeletons. The exoskeletons and assistive devices may be embedded with the linkage and other mechanisms to imitate the behavior of human lower limb. However, these mechanisms are synthesized using the complex conventional procedures. Thus, a new gait-inspired algorithm is proposed in this study for synthesizing a four-bar mechanism for exoskeletons.Methods: This paper presents a design of four-bar linkage for lower limb exoskeleton to support walking. A new gait-inspired algorithm to synthesize four-bar linkage is also proposed which uses two phases of gait, namely, the swing phase and the stance phase, for lower limb exoskeleton. The trajectory is derived for each phase of the gait and is combined with the optimization techniques. The trajectory passes through 10 precision points in each phase giving a total of 20 precision points for one gait cycle. The optimization is performed in two stages. The first stage deals with the minimization of error between the desired and the generated foot trajectories; whereas, the second stage deals with the minimization of error between the desired and generated hip trajectories of the linkage. Besides the gait-inspired four-bar linkage synthesis, a hybrid teaching-learning-particle-swarm-optimization (HTLPSO) technique is also used to solve the problem.Results: A well-established genetic algorithm (GA) and a new hybrid (HTLPSO) algorithm are used to compare the results of the tracking error of the linkage. It is found that the HTLPSO optimization algorithm performs better in comparison to GA for the problem considered here. Finally, a solid model of the proposed design for lower limb exoskeleton is presented. Moreover, the obtained linkage tracks all the prescribed points accurately and the simulation of designed linkage has been demonstrated using stick diagram for one gait cycle.Conclusion: The proposed method has simplified the synthesis procedure to a great extent, and a feasible design is obtained using the optimization algorithm. The mechanism obtained using the proposed method can walk smoothly which is validated through stick diagram. The proposed mechanism can be used for exoskeleton, assistive devices, bipeds etc. Moreover, the proposed method may be extended to six- and eight-bar mechanisms.

Hydrodynamics Banten Bay During Transitional Seasons (August-September) (Hidrodinamika Perairan Teluk Banten Pada Musim Peralihan (Agustus–September))

Perairan Teluk Banten merupakan wilayah yang sibuk dengan aktivitas wisata bahari, industri, permukiman dan lain-lain. Kondisi tersebut dapat menimbulkan dampak-dampak negatif seperti pencemaran, erosi, dan masalah lingkungan lainya. Pemahaman mengenai kondisi hidro-oseanografi sangat penting sebagai langkah untuk pengelolaan dan perlindungan wilayah pesisir dan laut. Tujuan dari penelitian ini untuk mengetahui karakteristik hidrodinamika di Perairan Teluk Banten pada musim peralihan (Agustus - September) berdasarkan data primer (data satu bulan arus, pasang surut, suhu) dan data sekunder (batimetri, kualitas air dan nutrient). Simulasi model diolah menggunakan MIKE 21, didukung dengan penggunaan CD-Oceanography. Hasil pengolahan data menunjukkan bahwa pola arus di Perairan Teluk Banten didominasi arus pasut dengan kecepatan berkisar antara 0-0,41 m.s-1, ditunjukkan oleh hasil pengolahan dalam bentuk stick diagram dan scatter plot yang menunjukkan pergerakan arus cenderung teratur dan arah arus dominan menuju ke arah Tenggara dan Selatan, hal ini juga didukung dengan hasil Current rose dengan menggunakan software WR plot. Kecepatan arus di permukaan lebih besar dan menyebar dibanding kecepatan arus di dekat dasar perairan. Simulasi arus permukaan (nilai error MRSE 12,25 %) menunjukkan bahwa arus bergerak sesuai dengan pengaruh pasang dan surut dengan kecepatan berkisar antara 0-0,42 m.s-1. Simulasi juga memperlihatkan distribusi konsentrasi nutrient dan kualitas perairan dipengaruhi oleh karakteristik hidrodinamika Teluk Banten.

UPWARD JUMP OF A BIPED

This paper explores the vertical upward jumping of a planar biped. There are two stance phases and one flight phase in the jump. One stance phase takes place before the flight phase, another one after the flight phase. The stance phase before the flight phase is decomposed into several parts: A crouching, a thrust at the knees, a rotation of both feet (massless) around their toes. The second stance phase (after the flight phase) starts with a touchdown of the toes. It consists of a feet rotation, a touchdown of the whole soles and finally of a straightening up movement of the biped. A mathematical model for this kind of jump is developed. Torques are applied at the hip, knee and ankle joints. The control algorithm is designed to ensure the jump of the biped. The synthesis of the jumping process is supported by simulation, which gives consistent results with human data from biomechanical literature. The stick diagram of the jump derived from simulation results seems natural for the human jumping.