Source code for sympy.physics.vector.point

from __future__ import print_function, division
from .vector import Vector, _check_vector
from .frame import _check_frame

__all__ = ['Point']


[docs]class Point(object): """This object represents a point in a dynamic system. It stores the: position, velocity, and acceleration of a point. The position is a vector defined as the vector distance from a parent point to this point. """ def __init__(self, name): """Initialization of a Point object. """ self.name = name self._pos_dict = {} self._vel_dict = {} self._acc_dict = {} self._pdlist = [self._pos_dict, self._vel_dict, self._acc_dict] def __str__(self): return self.name __repr__ = __str__ def _check_point(self, other): if not isinstance(other, Point): raise TypeError('A Point must be supplied') def _pdict_list(self, other, num): """Creates a list from self to other using _dcm_dict. """ outlist = [[self]] oldlist = [[]] while outlist != oldlist: oldlist = outlist[:] for i, v in enumerate(outlist): templist = v[-1]._pdlist[num].keys() for i2, v2 in enumerate(templist): if not v.__contains__(v2): littletemplist = v + [v2] if not outlist.__contains__(littletemplist): outlist.append(littletemplist) for i, v in enumerate(oldlist): if v[-1] != other: outlist.remove(v) outlist.sort(key=len) if len(outlist) != 0: return outlist[0] raise ValueError('No Connecting Path found between ' + other.name + ' and ' + self.name)
[docs] def a1pt_theory(self, otherpoint, outframe, interframe): """Sets the acceleration of this point with the 1-point theory. The 1-point theory for point acceleration looks like this: ^N a^P = ^B a^P + ^N a^O + ^N alpha^B x r^OP + ^N omega^B x (^N omega^B x r^OP) + 2 ^N omega^B x ^B v^P where O is a point fixed in B, P is a point moving in B, and B is rotating in frame N. Parameters ========== otherpoint : Point The first point of the 1-point theory (O) outframe : ReferenceFrame The frame we want this point's acceleration defined in (N) fixedframe : ReferenceFrame The intermediate frame in this calculation (B) Examples ======== >>> from sympy.physics.vector import Point, ReferenceFrame >>> from sympy.physics.vector import Vector, dynamicsymbols >>> q = dynamicsymbols('q') >>> q2 = dynamicsymbols('q2') >>> qd = dynamicsymbols('q', 1) >>> q2d = dynamicsymbols('q2', 1) >>> N = ReferenceFrame('N') >>> B = ReferenceFrame('B') >>> B.set_ang_vel(N, 5 * B.y) >>> O = Point('O') >>> P = O.locatenew('P', q * B.x) >>> P.set_vel(B, qd * B.x + q2d * B.y) >>> O.set_vel(N, 0) >>> P.a1pt_theory(O, N, B) (-25*q + q'')*B.x + q2''*B.y - 10*q'*B.z """ _check_frame(outframe) _check_frame(interframe) self._check_point(otherpoint) dist = self.pos_from(otherpoint) v = self.vel(interframe) a1 = otherpoint.acc(outframe) a2 = self.acc(interframe) omega = interframe.ang_vel_in(outframe) alpha = interframe.ang_acc_in(outframe) self.set_acc(outframe, a2 + 2 * (omega ^ v) + a1 + (alpha ^ dist) + (omega ^ (omega ^ dist))) return self.acc(outframe)
[docs] def a2pt_theory(self, otherpoint, outframe, fixedframe): """Sets the acceleration of this point with the 2-point theory. The 2-point theory for point acceleration looks like this: ^N a^P = ^N a^O + ^N alpha^B x r^OP + ^N omega^B x (^N omega^B x r^OP) where O and P are both points fixed in frame B, which is rotating in frame N. Parameters ========== otherpoint : Point The first point of the 2-point theory (O) outframe : ReferenceFrame The frame we want this point's acceleration defined in (N) fixedframe : ReferenceFrame The frame in which both points are fixed (B) Examples ======== >>> from sympy.physics.vector import Point, ReferenceFrame, dynamicsymbols >>> q = dynamicsymbols('q') >>> qd = dynamicsymbols('q', 1) >>> N = ReferenceFrame('N') >>> B = N.orientnew('B', 'Axis', [q, N.z]) >>> O = Point('O') >>> P = O.locatenew('P', 10 * B.x) >>> O.set_vel(N, 5 * N.x) >>> P.a2pt_theory(O, N, B) - 10*q'**2*B.x + 10*q''*B.y """ _check_frame(outframe) _check_frame(fixedframe) self._check_point(otherpoint) dist = self.pos_from(otherpoint) a = otherpoint.acc(outframe) omega = fixedframe.ang_vel_in(outframe) alpha = fixedframe.ang_acc_in(outframe) self.set_acc(outframe, a + (alpha ^ dist) + (omega ^ (omega ^ dist))) return self.acc(outframe)
[docs] def acc(self, frame): """The acceleration Vector of this Point in a ReferenceFrame. Parameters ========== frame : ReferenceFrame The frame in which the returned acceleration vector will be defined in Examples ======== >>> from sympy.physics.vector import Point, ReferenceFrame >>> N = ReferenceFrame('N') >>> p1 = Point('p1') >>> p1.set_acc(N, 10 * N.x) >>> p1.acc(N) 10*N.x """ _check_frame(frame) if not (frame in self._acc_dict): if self._vel_dict[frame] != 0: return (self._vel_dict[frame]).dt(frame) else: return Vector(0) return self._acc_dict[frame]
[docs] def locatenew(self, name, value): """Creates a new point with a position defined from this point. Parameters ========== name : str The name for the new point value : Vector The position of the new point relative to this point Examples ======== >>> from sympy.physics.vector import ReferenceFrame, Point >>> N = ReferenceFrame('N') >>> P1 = Point('P1') >>> P2 = P1.locatenew('P2', 10 * N.x) """ if not isinstance(name, str): raise TypeError('Must supply a valid name') if value == 0: value = Vector(0) value = _check_vector(value) p = Point(name) p.set_pos(self, value) self.set_pos(p, -value) return p
[docs] def pos_from(self, otherpoint): """Returns a Vector distance between this Point and the other Point. Parameters ========== otherpoint : Point The otherpoint we are locating this one relative to Examples ======== >>> from sympy.physics.vector import Point, ReferenceFrame >>> N = ReferenceFrame('N') >>> p1 = Point('p1') >>> p2 = Point('p2') >>> p1.set_pos(p2, 10 * N.x) >>> p1.pos_from(p2) 10*N.x """ outvec = Vector(0) plist = self._pdict_list(otherpoint, 0) for i in range(len(plist) - 1): outvec += plist[i]._pos_dict[plist[i + 1]] return outvec
[docs] def set_acc(self, frame, value): """Used to set the acceleration of this Point in a ReferenceFrame. Parameters ========== value : Vector The vector value of this point's acceleration in the frame frame : ReferenceFrame The frame in which this point's acceleration is defined Examples ======== >>> from sympy.physics.vector import Point, ReferenceFrame >>> N = ReferenceFrame('N') >>> p1 = Point('p1') >>> p1.set_acc(N, 10 * N.x) >>> p1.acc(N) 10*N.x """ if value == 0: value = Vector(0) value = _check_vector(value) _check_frame(frame) self._acc_dict.update({frame: value})
[docs] def set_pos(self, otherpoint, value): """Used to set the position of this point w.r.t. another point. Parameters ========== value : Vector The vector which defines the location of this point point : Point The other point which this point's location is defined relative to Examples ======== >>> from sympy.physics.vector import Point, ReferenceFrame >>> N = ReferenceFrame('N') >>> p1 = Point('p1') >>> p2 = Point('p2') >>> p1.set_pos(p2, 10 * N.x) >>> p1.pos_from(p2) 10*N.x """ if value == 0: value = Vector(0) value = _check_vector(value) self._check_point(otherpoint) self._pos_dict.update({otherpoint: value}) otherpoint._pos_dict.update({self: -value})
[docs] def set_vel(self, frame, value): """Sets the velocity Vector of this Point in a ReferenceFrame. Parameters ========== value : Vector The vector value of this point's velocity in the frame frame : ReferenceFrame The frame in which this point's velocity is defined Examples ======== >>> from sympy.physics.vector import Point, ReferenceFrame >>> N = ReferenceFrame('N') >>> p1 = Point('p1') >>> p1.set_vel(N, 10 * N.x) >>> p1.vel(N) 10*N.x """ if value == 0: value = Vector(0) value = _check_vector(value) _check_frame(frame) self._vel_dict.update({frame: value})
[docs] def v1pt_theory(self, otherpoint, outframe, interframe): """Sets the velocity of this point with the 1-point theory. The 1-point theory for point velocity looks like this: ^N v^P = ^B v^P + ^N v^O + ^N omega^B x r^OP where O is a point fixed in B, P is a point moving in B, and B is rotating in frame N. Parameters ========== otherpoint : Point The first point of the 2-point theory (O) outframe : ReferenceFrame The frame we want this point's velocity defined in (N) interframe : ReferenceFrame The intermediate frame in this calculation (B) Examples ======== >>> from sympy.physics.vector import Point, ReferenceFrame >>> from sympy.physics.vector import Vector, dynamicsymbols >>> q = dynamicsymbols('q') >>> q2 = dynamicsymbols('q2') >>> qd = dynamicsymbols('q', 1) >>> q2d = dynamicsymbols('q2', 1) >>> N = ReferenceFrame('N') >>> B = ReferenceFrame('B') >>> B.set_ang_vel(N, 5 * B.y) >>> O = Point('O') >>> P = O.locatenew('P', q * B.x) >>> P.set_vel(B, qd * B.x + q2d * B.y) >>> O.set_vel(N, 0) >>> P.v1pt_theory(O, N, B) q'*B.x + q2'*B.y - 5*q*B.z """ _check_frame(outframe) _check_frame(interframe) self._check_point(otherpoint) dist = self.pos_from(otherpoint) v1 = self.vel(interframe) v2 = otherpoint.vel(outframe) omega = interframe.ang_vel_in(outframe) self.set_vel(outframe, v1 + v2 + (omega ^ dist)) return self.vel(outframe)
[docs] def v2pt_theory(self, otherpoint, outframe, fixedframe): """Sets the velocity of this point with the 2-point theory. The 2-point theory for point velocity looks like this: ^N v^P = ^N v^O + ^N omega^B x r^OP where O and P are both points fixed in frame B, which is rotating in frame N. Parameters ========== otherpoint : Point The first point of the 2-point theory (O) outframe : ReferenceFrame The frame we want this point's velocity defined in (N) fixedframe : ReferenceFrame The frame in which both points are fixed (B) Examples ======== >>> from sympy.physics.vector import Point, ReferenceFrame, dynamicsymbols >>> q = dynamicsymbols('q') >>> qd = dynamicsymbols('q', 1) >>> N = ReferenceFrame('N') >>> B = N.orientnew('B', 'Axis', [q, N.z]) >>> O = Point('O') >>> P = O.locatenew('P', 10 * B.x) >>> O.set_vel(N, 5 * N.x) >>> P.v2pt_theory(O, N, B) 5*N.x + 10*q'*B.y """ _check_frame(outframe) _check_frame(fixedframe) self._check_point(otherpoint) dist = self.pos_from(otherpoint) v = otherpoint.vel(outframe) omega = fixedframe.ang_vel_in(outframe) self.set_vel(outframe, v + (omega ^ dist)) return self.vel(outframe)
[docs] def vel(self, frame): """The velocity Vector of this Point in the ReferenceFrame. Parameters ========== frame : ReferenceFrame The frame in which the returned velocity vector will be defined in Examples ======== >>> from sympy.physics.vector import Point, ReferenceFrame >>> N = ReferenceFrame('N') >>> p1 = Point('p1') >>> p1.set_vel(N, 10 * N.x) >>> p1.vel(N) 10*N.x """ _check_frame(frame) if not (frame in self._vel_dict): raise ValueError('Velocity of point ' + self.name + ' has not been' ' defined in ReferenceFrame ' + frame.name) return self._vel_dict[frame]