About using PointActuator to simulate object weight

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Yuan Yuan
Posts: 26
Joined: Tue Nov 02, 2021 6:47 pm

About using PointActuator to simulate object weight

Post by Yuan Yuan » Mon Dec 04, 2023 2:34 am

Dear All,

I conducted some simulations of object lifting using hands; the locomotion type is stooping; during locomotion, the human model lift an object of 5kg with two hands. Specifcally, PointActuators are applied to simulate object gravity. The details are as follows:

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				<PointActuator name="object_l">
					<body>hand_l </body>
					<point> 0.00000000000000000000 0.00000000000000000000 0.00000000000000000000 </point>
					<point_is_global> false </point_is_global>
					<direction> 0.00000000000000000000 -1.00000000000000000000 -0.00000000000000000000 </direction>
					<force_is_global> true </force_is_global>
					<optimal_force> 1 </optimal_force>
				</PointActuator>
				<PointActuator name="object_r">
					<body>hand_r </body>
					<point> 0.00000000000000000000 0.00000000000000000000 0.00000000000000000000 </point>
					<point_is_global> false </point_is_global>
					<direction> 0.00000000000000000000 -1.00000000000000000000 -0.00000000000000000000 </direction>
					<force_is_global> true </force_is_global>
					<optimal_force> 1 </optimal_force>
				</PointActuator>
May I know whether the above definition of object weight is feasible?

Actually, the results of baseline (without object) and with object are compared; it showed that the back muscle force is larger in baseline condition. It is abnormal. Therefore, it seems that there should be problems about the modeling of object weight. Thanks. Yuan
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Nicholas Bianco
Posts: 1045
Joined: Thu Oct 04, 2012 8:09 pm

Re: About using PointActuator to simulate object weight

Post by Nicholas Bianco » Tue Dec 05, 2023 3:42 pm

Hi Yuan Yuan,

You do not need actuators to simulate gravity in a model. As long as your model defines gravity (you can check the gravity vector definition with Model::getGravity()), then gravitational forces will be applied to the model.

Best,
Nick
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