The effect of added inertia to the pelvis during walking.

Terpstra, W. (2011) The effect of added inertia to the pelvis during walking. thesis, Human Movement Sciences.

Text Terpstra.pdf Restricted to Registered users only Download (12MB)

Abstract

Robotics can provide flexible gait training for stroke survivors. 'Assistance as needed' (AAN) algorithms are developed to let the patients actively participate in the training and to facilitate recovery. The lower powered exoskeleton (LOPES} contains an AAN algorithm. Implementing this algorithm requires a 'walk freely' mode where the patient should be fully in charge. Therefore, the robot should display minimal impedance in order to not affect the patient's gait. However this is not the case in the LOPES due to impedances like inertia. In order to build a new robot (LOPES II) a redevelopment project has started. In this redevelopment project the requirements for a 'patient in charge mode' have to be set. Therefore, we are investigating the effects of inertia on the gait pattern. The aim of this study was to assess the effect of added inertia (<15% body weight) to the pelvis on gait parameters. Nine healthy subjects walked on a treadmill with an adjustable inertia mechanism attached to their waist. The treadmill speed was varied systematically {1.5 and 4.5 km/h) as well as the inertia in the lateral direction (0.7 kg, 3.0 kg and 7.1 kg) and anterior posterior direction (0. 7 kg, 3.8 kg and 10.1 kg), resulting in 18 conditions. We added control conditions without the added loads at the two different speeds. After a familiarization period we measured two minutes per condition the (I) spatial and temporal gait parameters, (II) limb kinematics (ROM in pelvis, knee, ankle joints and segment centre of mass (COM) displacement and acceleration of the pelvis), (Ill) electromyography (RMS of the gluteus maximus, gluteus medius, rectus femoris, vastus lateralis, biceps femoris, soleus, gastrocnemius medialis and the tibialis anterior) and {IV) energy expenditure (V02, V02 per kg, V'E, V'E/V02 and the HR). The results showed that the spatiotemporal gait parameters and energy expenditure did not differed significantly when added inertia was applied. The ranges of motions (ROM) of the pelvis joint angles were decreased in sagittal plane (F(2,6)=10.90; p<0.05) and frontal plane (F(2,6)=7.79,p<O.OS) when inertia was applied in the anterior-posterior direction. The range of the pelvis segment COM displacement (F(2,6}=21.02,p<O.OS) and the fore aft range of the segment COM acceleration (F=8.57, df=2.6, p<0.05} decreased when inertia was applied in anterior-posterior direction and lateral range decreased (F=6.93, df=2.6, p<0.05) when inertia was applied from the lateral side. The significant parameters, except for the ROM of the pelvis joint angles and lateral acceleration of the pelvis, exceeded the maximum criterion of 10% difference when inertia was applied in the anterior-posterior direction relative walking freely. To relate this to the requirement for the 'patient in charge' mode in the LOPES II, more than 10kg reflected inertia on the pelvis would not be advised. The patient's gait pattern will be affected and therefore the 'patient in charge' mode will not resemble free walking. Besides, when more than 10% inertia (approximately 10 kg) is added the patient could feel the robot presence because it exceeds just notable differences for inertia. In conclusion, the maximum weight for an exoskeleton will be 10kg projected on the pelvis in order resemble free walking in the 'patient in charge' mode.

Item Type:	Thesis (Thesis)
Supervisor name:	?
Faculty:	Medical Sciences
Date Deposited:	25 Jun 2020 11:03
Last Modified:	25 Jun 2020 11:03
URI:	https://umcg.studenttheses.ub.rug.nl/id/eprint/2282

Actions (login required)

View Item