Kinematics models and DH parameters

This page shows the three ways to get the geometry of a Yaskawa Motoman arm for the offline kinematics of the SDK: the catalog of 169 models, the ALL.PRM parameter file of the controller, or your own DH parameters. It also explains the meaning of each parameter.

DH parameters

DhParameters holds the 9 values that change from one 6-axis Yaskawa arm to another. The other values of the Denavit-Hartenberg table are the same for every arm.

The parameters use the modified DH convention (Craig). KinematicsCategory tells which solver is used: Opw when D5 is 0, J5OffsetWrist otherwise.

From the catalog

ArmKinematicModels lists 169 models: GP (33), MH (48), ES (14), SP (14), HC (15), HP (7), AR (6), MS (6), PH (5), MotoMINI and others. FromArmKinematicModel returns their parameters. FromArmKinematicModelName finds a model by its name, and returns null when the name is not known.

static void Main()
{
// From the enumeration: 169 models of the catalog
DhParameters gp7 = DhParameters.FromArmKinematicModel(ArmKinematicModels.GP7);

// From the name of the model, case ignored. Null if the model is not known.
DhParameters hc10 = DhParameters.FromArmKinematicModelName("HC10");

Console.WriteLine(gp7);  // A1=40, A2=445, A3=40, D4=440, D5=0, D6=80...
Console.WriteLine(gp7.KinematicsCategory);  // Opw
Console.WriteLine(hc10.KinematicsCategory); // J5OffsetWrist

// Every model of the catalog
foreach (ArmKinematicModels model in Enum.GetValues(typeof(ArmKinematicModels)))
    Console.WriteLine(model);
}
}

Some models have several variants, with the order code in the name (for example HC10DT_1_06VXHC10_B10). Use the variant of the name plate of your robot. Do not store the integer value of the enumeration: new models are added in alphabetical order and shift the values. Store the name.

From the controller

The ALL.PRM file of a controller contains the geometry of its robot. FromPrmFile reads a file saved on the PC, FromPrmContent the text of the file. DX100, DX200, FS100, YRC1000 and YRC1000micro files are supported. The parameters of the first robot (R1) are read.

static void Main()
{
// ALL.PRM saved from the controller, on the PC
DhParameters fromFile = DhParameters.FromPrmFile(@"C:\Backup\ALL.PRM");

// Or downloaded from the controller (1.4 MB, about 13 s on a YRC1000micro)
var parameters = new ConnectParameters("192.168.0.1");
parameters.Ftp.Enable = true;
var robot = new YaskawaRobot();
robot.Connect(parameters);

string content = robot.Ftp.GetFile("ALL.PRM");
DhParameters dh = DhParameters.FromPrmContent(content);

// Joint solutions of the current position (tool 0, robot frame)
var position = robot.HighSpeedEServer.GetRobotCartesianPosition();
foreach (JointsAngles solution in KinematicsUtils.InverseKinematics(position, dh))
    Console.WriteLine(solution);

robot.Disconnect();
}
}

Download ALL.PRM with FTP, HTTP or the High Speed Ethernet Server. The file is about 1.4 MB: FTP and HTTP take about 13 s on a YRC1000micro, the High Speed Ethernet Server about 45 s. Save it once, then use FromPrmFile.

On a MotoMINI, the parameters read from ALL.PRM are equal to ArmKinematicModels.MotoMINI of the catalog. The file is the right choice for a model that is not in the catalog, or to check the model of a robot.

A file of a robot with a structure that is not supported throws a NotSupportedException. See Supported robots.

Your own values

The constructor takes A1, A2, A3, D4, D5, D6 in mm, then Theta2, Theta3, Theta5 in degrees. Two DhParameters with the same values are equal.

static void Main()
{
// A1, A2, A3, D4, D5, D6 in mm, then Theta2, Theta3, Theta5 in degrees
var dh = new DhParameters(40, 445, 40, 440, 0, 80, -90, 0, 0);

// Same values as the catalog: the same geometry
bool sameAsGp7 = dh.Equals(DhParameters.FromArmKinematicModel(ArmKinematicModels.GP7));

// The solver is chosen from the values: D5 = 0 is a spherical wrist
Console.WriteLine(dh.KinematicsCategory); // Opw
}
}

DhParameters implements IDhParameters: your own class can also implement this interface and be passed to KinematicsUtils.

Reference

What to read next

• Offline kinematics: forward and inverse kinematics.
• FTP file transfers: download ALL.PRM and the other files of the controller.