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Table 1 Definition of mathematical terms for the complex model

From: Experimental investigation of efficient locomotion of underwater snake robots for lateral undulation and eel-like motion patterns

Symbol

Description

Vector

n

The number of links

 

l

The half length of a link

 

m

Mass of each link

 

J

Moment of inertia of each link

 

\(\theta _{i}\)

Angle between link i and the global x axis

\({\varvec{\theta }}\) \(\in \mathbb {R}^n\)

\(\phi _{i}\)

Angle of joint i

\({\varvec{\phi }}\) \(\in \mathbb {R}^{n-1}\)

\((x_i, y_i)\)

Global coordinates of the CM of link i

\(\mathbf {X},\mathbf {Y}\) \(\in \mathbb {R}^n\)

\((p_x, p_y)\)

Global coordinates of the CM of the robot

\(\mathbf {p}_\text {{CM}}\) \(\in \mathbb {R}^2\)

\(u_{i}\)

Actuator torque of joint between link i and link \(i+1\)

\(\mathbf {u}\) \(\in \mathbb {R}^{n-1}\)

\(u_{i-1}\)

Actuator torque of joint between link i and link \(i-1\)

\(\mathbf {u}\) \(\in \mathbb {R}^{n-1}\)

\(f_{x,i}\)

Fluid force on link i in x direction

\({\mathbf {f_{x}}}\) \(\in \mathbb {R}^n\)

\(f_{y,i}\)

Fluid force on link i in y direction

\({\mathbf {f_{y}}}\) \(\in \mathbb {R}^n\)

\(\tau _i\)

Fluid torque on link i

\({\varvec{\tau }} \in \mathbb {R}^n\)

\(h_{x,i}\)

Joint constraint force in x direction on link i from link \(i+1\)

\({\mathbf {h_{x}}}\) \(\in \mathbb {R}^{n-1}\)

\(h_{y,i}\)

Joint constraint force in y direction on link i from link \(i+1\)

\({\mathbf {h_{y}}}\) \(\in \mathbb {R}^{n-1}\)

\(h_{x,i-1}\)

Joint constraint force in x direction on link i from link \(i-1\)

\({\mathbf {h_{x}}}\) \(\in \mathbb {R}^{n-1}\)

\(h_{y,i-1}\)

Joint constraint force in y direction on link i from link \(i-1\)

\({\mathbf {h_{y}}}\) \(\in \mathbb {R}^{n-1}\)