One issue you may be having is the mixture of sympy.vector,
sympy.physics.vector, and sympy.geometry. These packages are not designed
to work with each other currently. I recommend sticking to one of those
depending on what you are trying to do.
moorepants.info
+01 530-601-9791
On Mon, Jul 17, 2017 at 11:11 AM, <shoulddt...@gmail.com> wrote:
> Hello all,
> I am trying to use Sympy to model a multi-body dynamic system. I am trying
> to create the required points and coordinate systems to model the system in
> 3d. I am running into trouble creating symbolic points in 3 dimensions. I
> can create the points as shown below, but whenever I attempt to perform a
> math operation on the points, such as deriving the midpoint or distance, I
> receive an error saying that "Point" is an unsupported type, or that the
> "Point" has no x-attribute.
>
> What is the correct method for declaring a 3 dimensional point
> symbolically, so that you can reference each component of it and perform
> operations to it? After declaring the point, I need to use the .set_pos
> function or an equivalent function to declare the position of the points.
>
> from __future__ import print_function, division
> from sympy import symbols, simplify, Segment
> from sympy.geometry import Point3D
> from sympy.vector import *
> from sympy.physics.mechanics import dynamicsymbols, ReferenceFrame, Point
> from sympy.physics.vector import init_vprinting
> init_vprinting(use_latex='mathjax', pretty_print=False)
>
> # Declare reference frames
> inertial_frame = ReferenceFrame('inertial_frame')
> Chassis_frame = ReferenceFrame('Chassis_frame')
> LUCA_frame = ReferenceFrame('LUCA_frame')
>
> # Define the rotation angle symbols
> thRoll, thPitch, thYaw = dynamicsymbols('thRoll, thPitch, thYaw')
> thLUCAy = symbols('thLUCAy') ; thLUCAz = symbols('thLUCAz')
> thLUCAx, thLLCAx, thRUCAx, thRLCAx = dynamicsymbols('thLUCAx, thLLCAx,
> thRUCAx, thRLCAx')
>
>
> # Define Position Components
> ChassisDeltax = symbols('ChassisDeltax')
> ChassisDeltay = symbols('ChassisDeltay')
> ChassisDeltaz = symbols('ChassisDeltaz')
> CGposx = symbols('CGposx')
> CGposy = symbols('CGposy')
> CGposz = symbols('CGposz')
> LUCAMPx = symbols('LUCAMPx')
> LUCAMPy = symbols('LUCAMPy')
> LUCAMPz = symbols('LUCAMPz')
>
> # Set Positions
> ChassisC.set_pos(GlobalCoord0,(ChassisDeltax * inertial_frame.x +
> ChassisDeltay * inertial_frame.y + ChassisDeltaz * inertial_frame.z))
> CGpos.set_pos(ChassisC,(CGposx * Chassis_frame.x + CGposy *
> Chassis_frame.y + CGposz * Chassis_frame.z))
> LUCAMP.set_pos(ChassisC,(LUCAMPx * Chassis_frame.x + LUCAMPy *
> Chassis_frame.y + LUCAMPz * Chassis_frame.z))
>
> # Center of Mass Locations
> CoM_Chassis = Point('CoM_Chassis')
> CoM_Chassis.set_pos(CGpos,0)
> CoM_LUCA = Point('CoM_LUCA')
> CoM_LUCA.set_pos(LUCAMP, ((LUCA_xOff / 2) * LUCA_frame.x + (LUCA_L / 2) *
> LUCA_frame.y + 0 * LUCA_frame.z))
>
>
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