Ontology Parameters:

RM75 Series Parameters and D-H Model

Basic Parameters

Parameter Name		Parameter Value
Basic Parameters	Degrees of Freedom	7
	Configuration	Humanoid Configuration
	Joint Brake Type	Joints 1 to 4: Hard Brake Joints 5 to 7: Soft Brake
	Working Radius/mm	Standard Version: 610 Six-Axis Force Version: 638.5
	Payload/kg	5
	Self-weight/kg	Standard Version: 7.8 Six-Axis Force Version: 7.9
	Repeatability/mm	±0.05
	TCP Line Speed/m/s	≤1.8
	Typical Power/W	≤100
	Peak Power/W	≤200
	Installation Angle	Any Angle
	Base Dimensions/mm	φ107
	Material	Aluminum Alloy/ABS
Environmental Adaptability	Operating Temperature/℃	0-45
	Operating Humidity	25~85% Non-condensing
	Protection Level	Body IP54
Motion Angle Range/°	J1	-178~+178
	J2	-130~+130
	J3	-178~+178
	J4	-135~+135
	J5	-178~+178
	J6	-128~+128
	J7	-360~+360
Maximum Angular Velocity/°/s	J1	180
	J2	180
	J3	225
	J4	225
	J5	225
	J6	225
	J7	225
Force Control Specifications	Six-Axis Force Range	Standard Version: - Six-Axis Force Version: 200N/7N·m
	Six-Axis Force Accuracy	Standard Version: - Six-Axis Force Version: ＜0.5%FS

Ontology Parameters

MDH model frame:

MDH parameters of RM75 (modified D-H parameters):

joint_id(i)	$a_{i-1}$(mm)	${\alpha }_{i-1}$(°)	$d_i$(mm)	offset(°)
1	0	0	240.5	0
2	0	-90	0	0
3	0	90	256	0
4	0	-90	0	0
5	0	90	210	0
6	0	-90	0	0
7	0	90	$d_7$	0

• RM75-B  : $d_7=144$ mm
• RM75-6F: $d_7=172.5$ mm

Note: offset refers to the offset of the joint zero position from the model zero position, that is, model angle = joint angle + offset.

Kinetic parameters of RM75 robot link

joint_id(i)	1	2	3	4	5	6	7	-
$m$	1.574	1.217	1.11	0.685	0.619	0.602	0.107	0.248
$x$	0.241	-0.357	0.003	-0.005	0.078	-0.014	-0.506	-0.426
$y$	-13.273	-106.798	-10.398	-84.658	-12.937	-78.524	0.255	0.237
$z$	-9.95	5.329	-11.324	4.747	-8.781	2.819	-10.801	-27.223
$L_{xx}$	2920.666	17404.207	2099.034	6204.576	778.615	4499.867	50.918	308.844
$L_{xy}$	14.703	-43.488	2.292	-0.819	2.261	-0.802	-3.136	-3.781
$L_{xz}$	-4.131	-3.297	-4.181	-0.615	-0.921	-0.444	-0.699	-1.468
$L_{yy}$	2476.942	927.428	1641.235	388.441	590.169	294.76	47.42	304.616
$L_{yz}$	-28.462	108.523	-93.542	43.054	-35.324	12.831	0.388	0.888
$L_{zz}$	1727.926	17319.77	1182.557	6162.881	473.863	4478.261	60.35	122.62
Remarks							B	6F

Description:

• $m$ is the mass of the link, $kg$
• $x$ is the x-coordinate of the center of mass of link, $mm$
• $y$ is the y-coordinate of the center of mass of link, $mm$
• $z$ is the z-coordinate of the center of mass of link, $mm$
• $L_{xx}$,$L_{xy}$,$L_{xz}$,$L_{yy}$,$L_{yz}$,$L_{zz}$ is the principal moment of inertia described in the link frame, $kg·mm²$
• B: standard version, 6F: six-axis force version

Remarks:

• Source of data: CAD design values.
• If the inertial parameters in the center of mass frame are required, they can be calculated based on the parallel axis theorem, as stated below.

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Assuming there is an output frame $\{i\}$, the center of mass frame coinciding with this coordinate system $\{i\}$ is $\{c\}$, and the coordinates of the center of mass in this frame $\{i\}$ are $P_c=[x_c,y_c,z_c{]}^T$, then according to the parallel axis theorem:

$$I_c=L_i-m(P_c^T{P}_c{I}_{3\times 3}-P_c{P}_c^T)$$

Where,

$$L_i=\left[\begin{array}{ccc}{L}_{xx}& L_{xy}& L_{xz}\\ L_{xy}& L_{yy}& L_{yz}\\ L_{xz}& L_{yz}& L_{zz}\end{array}\right]$$

Distribution and dimensions of joints

The RM75 humanoid robotic arm has seven rotating joints, each of which represents one degree of freedom. As shown in the figure below, robot joints include the shoulders (joint 1, joint 2, and joint 3), elbow (joint 4), and wrists (joint 5, joint 6, and joint 7).

Workspace

The workspace of RM75-B is a sphere with a working radius of 610 mm, in addition to the cylindrical space directly above and below the base. When determining the installation position of the robot, due considerations must be given to the cylindrical space directly above and below the robot, to avoid moving tools to this cylindrical space as much as possible. Furthermore, in actual applications, the motion ranges of all joints are as follows: joint 1: ±178°; joint 2: ±130°; joint 3: ±178°; joint 4: ±135°; joint 5: ±178°; joint 6: ±128°; joint 7: ±360°.

Seen from the cross-section of the workspace, the area with good maneuverability of the 7-axis robot is as indicated by the yellow dotted line in the following figure, an annular area in the workspace as a whole.

Motion singularities

Shoulder singularity

Co-line of wrist center point C (axis intersection of joint 6 and joint 7) with axis of joint 1, indicated point [0,43.4,0,-105.7,0,-30,0], as shown in the figure below:

The special situation of co-axis of joint 1 with joint 7, and co-line of point C with axis of joint 1, indicated point [0,43.4,0,-105.7,0,62.3,0], as shown in the figure below:

Elbow singularity

q4=0, i.e. the point format is [x,x, x,0,x,x,x], indicated point [0,30,0,0,90,90,0], as shown in the figure below:

q2=0, q4=0 (a special situation of q4=0), i.e. the point format is [x,0,x,0,x,x,x], indicated point [0,0,0,0,90,90,0], as shown in the figure below:

Wrist singularity

Co-axis of joint 5 and joint 7, q6=0, i.e. the point format is [x,x,x,x,x,0,x], indicated point [0,30,0,60,90,0,0], as shown in the figure below:

q2=0, q6=0 (a special situation of q6=0), i.e. the point format is [x,0,x,x,x,0,x], indicated point [0,0,0,60,90,0,0], as shown in the figure below:

q4=0, q6=0 (a special situation of q6=0), i.e. the point format is [x,x,x,0,x,0,x], indicated point [0,30,0,0,90,0,0], as shown in the figure below:

Boundary singularity

When the end of robotic arm reaches the farthest end, q4=0, q6=0 (a special situation of q4=0), i.e. the point format is [x,x,x,0,x,0,x], indicated points [0,0,0,0,0,0], [0,45,45,0,45,0,45], as shown in the figure below:

Load curves

Represent the end load curves of RM75-B and RM75-6F. Where, L refers to the radial distance of the center of mass of end load against the plane of end flange, and Z refers to the normal distance of the center of mass of end load against the plane of end flange.