constants.py

"""
Constants used accross multiple project files.
Not expected to be changed frequently.
"""

from dataclasses import dataclass
import numpy as np
import config

g = 9.81

EPSILON = 0.001
IN_TO_M = 0.0254
v_stiction=1e-3

# Dimensions of physical pieces
THIN_PLYWOOD_THICKNESS = IN_TO_M*3/8
THICK_PLYWOOD_THICKNESS = IN_TO_M*3/4
PLYWOOD_LENGTH = IN_TO_M*12
PLYWOOD_DENSITY = 500 # kg/m^3

Nm__PER_InLb = 0.112984833 # McMaster uses imperial units to a fault
def stiffness_Nm_per_Rad(num_links: config.NumLinks):
    if num_links == config.NumLinks.TWO:
        stiffness__InLb_per_Rad__2_links = 6*0.55/(np.pi)
        return Nm__PER_InLb*stiffness__InLb_per_Rad__2_links
    if num_links == config.NumLinks.FOUR:
        stiffness__InLb_per_Rad__4_links = 40/(np.pi)
        return Nm__PER_InLb*stiffness__InLb_per_Rad__4_links

def PEDESTAL_X_DIM(num_links: config.NumLinks):
    if num_links == config.NumLinks.TWO:
        return PLYWOOD_LENGTH/2
    if num_links == config.NumLinks.FOUR:
        return PLYWOOD_LENGTH/4

@dataclass
class SystemConstants:
    """
    Constants for this particular plant + manipulator
    """
    w_L: float
    h_L: float
    m_L: float
    m_M: float
    b_J: float
    k_J: float
    mu: float
    r: float

def nominal_sys_consts(num_links):
    return SystemConstants(
        w_L = PEDESTAL_X_DIM(num_links),
        h_L = THIN_PLYWOOD_THICKNESS,
        m_L = PLYWOOD_LENGTH*PEDESTAL_X_DIM(num_links)*\
            THIN_PLYWOOD_THICKNESS*PLYWOOD_DENSITY,
        m_M = 1e-3,
        b_J = 0.035,
        k_J = 0.35,
        mu = 0.4,
        r = 0.05,
    )