The Port-Hamiltonian Structure of Vehicle Manipulator Systems
Authors: Ramy Rashad
Organizations: Control and Instrumentation Engineering department and Interdisciplinary Research Center for Smart Mobility and Logistics, King Fahd University of Petroleum and Minerals, Dhahran, 34464, Saudi Arabia
This paper presents a port-Hamiltonian formulation of vehicle-manipulator systems (VMS), a broad class of robotic systems including aerial manipulators, underwater manipulators, space robots, and omnidirectional mobile manipulators. Unlike existing Lagrangian formulations that obscure the underlying energetic structure, the proposed port-Hamiltonian formulation explicitly reveals the energy flow and conservation properties of these complex mechanical systems. We derive the port-Hamiltonian dynamics from first principles using Hamiltonian reduction theory. Two complementary formulations are presented: a standard form that directly exposes the energy structure, and an inertially-decoupled form that leverages the principal bundle structure of the VMS configuration space and is particularly suitable for control design and numerical simulation. The coordinate-free geometric approach we follow avoids singularities associated with local parameterizations of the base orientation. We rigorously establish the mathematical equivalence between our port-Hamiltonian formulations and existing reduced Euler-Lagrange and Boltzmann-Hamel equations found in the robotics and geometric mechanics literature.
Figures & tables
Figure 1: Illustration of vehicle-manipulator systems. Left figure shows a floating-base manipulator h∈Gb=SE(3) while the right figure shows a ground mobile manipulator h∈Gb=S1×R2 .
Map/Variable
Coordinate-free
Coordinate-based
(v,q˙)
gb×TqQm
Rb×Rn
(w,τ)
gb∗×Tq∗Qm
Rb×Rn
Jii,s(q)
gb×TqQm→gis
R6×(b+n)
Jii,b(q)
TqQm→gib
R6×n
Mb(q)
gb→gb∗
Rb×b
Mbm(q)
TqQm→gb∗
Rb×n
Table 1: Coordinate-free and coordinate-based representations of maps and variables in ( 21 )
Figure 2: Port-Hamiltonian formulation of fixed-base manipulator dynamics.
Figure 3: Port-Hamiltonian formulation of moving-base dynamics.
Map/Variable
Coordinate-free
Coordinate-based
(p˙,∂p∂Hkin)
gb∗×gb
Rb×Rb
(q˙,∂q∂Hkin)
TqQm×Tq∗Qm
Rn×Rn
(π˙,∂π∂Hkin)
Tq∗Qm×TqQm
Rn×Rn
adp∼
gb→gb∗
Rb×b
J(p)
Tx∗X→TxX
R(b+2n)×(b+2n)
G
gb∗×Tq∗Qm→TxX
R(b+2n)×(b+n)
Table 2: Coordinate-free and coordinate-based representations of maps and variables in ( 47 )
Figure 4: Principal bundle structure of the VMS configuration space Q=Gb×Qm .
Map
Coordinate-free
Coordinate-based
A(q)
TqQm→gb
Rb×n
Φ(p,q)
TxX→Tx^X
R(b+2n)×(b+2n)
L(p,q)
TqQm→Tq∗Qm
Rn×n
Nb(p^,q^)
Tq^Qm→gb
Rb×n
N^m(q^,π^)
Tq^Qm→Tq^∗Qm
Rn×n
B(p^,q^)
Tq^Qm→Tq^∗Qm
Rn×n
Table 3: Coordinate-free and coordinate-based representations of maps in ( 59 )
Figure 5: The proposed port-Hamiltonian formulations of VMS dynamics and their corresponding Dirac structures. Left figure shows the port-Hamiltonian formulation ( 47 ) while the right figure shows the inertially-decoupled port-Hamiltonian formulation ( 59 ). The intermediate figure illustrates the change of coordinates ϕ(q) .
Map
Coordinate-free
Coordinate-based
Pb(q,q˙)
gb→gb
Rb×b
Eb(v^,q)
TqQm→gb
Rb×n
C^m(q,q˙)
TqQm→Tq∗Qm
Rn×n
B^(v^,q^)
Tq^Qm→Tq^∗Qm
Rn×n
M^,C^1,C^2
gb×TqQm→gb∗×Tq∗Qm
R(b+n)×(b+n)
Table 4: Coordinate-free and coordinate-based representations of maps in ( 85 )