7.1.vsp.code: Vehicle Specific Power (VSP) related code

In pems.utils: Portable Emissions (and Other Mobile) Measurement System Utilities

Vehicle Specific Power (VSP) related code

Description

Functions associated with VSP calculations.

Usage

#calculation

calcVSP(speed = NULL, accel = NULL, slope = NULL, 
          time = NULL, distance = NULL, data = NULL,
          calc.method = calcVSP_JimenezPalacios,
          ..., fun.name = "calcVSP", this.call = NULL)

calcVSP_JimenezPalacios(speed = NULL, accel = NULL, 
          slope = NULL, vehicle.weight = NULL, vsp.a = NULL, 
          vsp.b = NULL, vsp.c = NULL, vsp.g = NULL, ..., 
          data = NULL,  
          fun.name = "calcVSP_JimenezPalacios", 
          this.call = NULL)

#VSP binning

refVSPBin(..., bin.method="ncsu.14")

refVSPBin_NCSU.14(vsp = NULL, data = NULL, 
          ..., fun.name="refVSPBin_NSCU.14")

refVSPBin_MOVES.23(vsp = NULL, speed = NULL, data = NULL, 
          ..., fun.name="refVSPBin_MOVES.23")
          
#vsp plotting

VSPPlot(vsp, em = NULL, ..., data = NULL, plot.type = 1, 
          fun.name="VSPPlot")

VSPBinPlot(vspbin, em = NULL, ..., data = NULL, 
          plot.type = 1, stat = NULL, fun.name="VSPBinPlot")
          

Arguments

speed, accel, slope, time, distance, vsp, vspbin, em	(Typically pems.element vectors) speed, accel, slope, time and distance are possible inputs for VSP calculation. vsp and speed are possible inputs for VSP binning methods. vsp, vspbin and em are x and y inputs for associated plots. (See Notes about inputs and methods.)
data	(Optional, typically pems) The data source for inputs.
calc.method, bin.method	(Required functions) calc.method is the function used to calculate VSP (default calcVSP_JimenezPalaciosCMEM). bin.method is the methods used when binning VSP measurements. (See Notes.)
...	(Optional) Other arguments, currently passed on as supplied to associated calculation or binning method, or back to pemsPlot.
fun.name	(Optional character) The name of the parent function, to be used in error messaging.
this.call	(Optional) Initial call, should generally be ignored. See common.calculations for further details.
vehicle.weight, vsp.a, vsp.b, vsp.c, vsp.g	(Numerics) VSP constants. If not supplied, defaults are applied. See Below.
plot.type	(Optional numeric) For VSPPlot and VSPBinPlot, the type of plot to generate. For VSPPlot, 1 a conventional scatter plot; or 2 a box-and-whisker plot. For VSPBinPlot, 1 a bar plot; or 2 a box-and-whisker plot.
stat	(Function) For VSPBinPlot, the statistic to use when calculating bar scales for plot.type 1. By default this is mean if em is supplied or count if not. NOTE: stat is ignore when plot.type is used

Details

calcVSP... functions calculate VSP:

calcVSP is a wrapper function which allows users to supply different combinations of inputs. VSP calculations typically require speed, acceleration and slope inputs. However, This wrapper allows different input combinations, e.g.:

time and distance (time and distance -> speed, time and speed -> accel)

time and speed (time and speed -> accel)

speed and accel

This then passes on speed, accel and (if supplied) slope to the method defined by calc.method. (This means other VSP functions run via calcVSP(..., calc.method = function) share this option without needed dedicated code.)

calcVSP_JimenezPalacios calculates VSP according to Jimenez Palacios methods. See References and Note below.

refVSPBin... functions generate a reference list of VSP bins:

refVSPBin is a wrapper that generates VSP Mode bins depending on method applied.

binVSP_NCSU.14 bins supplied vsp using the 14 bin method described in Frey et al 2002.

binVSP_MOVES.23 bins supplied vsp using that and speed and the 23 bin MOVES method (See Note).

VSPPlot generates various plots of VSP (x-axis) and emission (y-axis) data.

VSPBinPlot generates various plots of VSP binned data.

Value

calcVSP by default uses the Jimenez Palacios method to calculate VSP in kW/metric ton.

refVSPBin generates a pems.element factor vector of VSP Mode bin assignments.

VSPPlot and VSPBinPlot generate plots as lattice objects.

Note

calcVSP... constants can be set/modified in the calculation call, e.g. calcVSP(..., vsp.a = [new.value]). If not supplied, defaults are used. (See References.)

binVSP_MOVES.23 is in-development. Do not use without independent confirmation of values.

Unit handling in pems.utils is via checkUnits, getUnits, setUnits and convertUnits. See common.calculations for details.

Author(s)

Karl Ropkins

References

calcVSP_JimenezPalacios uses methods described in:

Jimenez-Palacios, J.L. (1999) Understanding and Quantifying Motor Vehicle Emissions with Vehicle Specific Power and TILDAS Remote Sensing. PhD Thesis, Massachusetts Institute of Technology, Cambridge, MA.

vehicle.weight is the vehicle mass (in metric tons), and vsp.a, vsp.b, vsp.c and vsp.g are the calculations constants for:

vsp = speed * (a * accel + (g * slope) + b) + (c * speed^3)

By default: a = 1.1, b = 0.132, c = 0.000302 and g = 0.132 (as of Jimenez-Palacios, 1999).

Method ONLY INTENDED FOR vehicles < 3.855 metric tons.

refVSPBin_NCSU.14 VSP binning as described in:

Frey, H.C., Unal, A., Chen, J., Li, S. and Xuan, C., 2002. Methodology for developing modal emission rates for EPA's multi-scale motor vehicle & equipment emission system. Ann Arbor, Michigan: US Environmental Protection Agency. (EPA420-R-02-027)

See Also

See common.calculations (and checkUnits and convertUnits) for details of data management.

Examples

###########
##example 1 
###########

#basic usage

vsp <- calcVSP(velocity, time = local.time, data = pems.1)
#where the returned object, vsp, is vsp values as pems.element

ncsu.14 <- refVSPBin(vsp)
#where the returned object, nscu.14, is the associated modal bin 
# assignments based on the Frey et al (2002) 14 bin method. 

pems.utils documentation built on April 3, 2025, 6:02 p.m.