BIG YAM

✓ Python SDK✓ MuJoCo Sim✓ Gravity Compensation✓ Heavy Payload

BIG YAM is the heaviest, highest-payload arm in the YAM family — a larger 6-DOF arm with DM6248 shoulder motors for substantially more torque, and a redesigned joint 2 with reversed direction. Use BIG YAM when YAM Standard / Pro / Ultra can't handle the payload or reach requirements.

For the full SDK reference and API documentation that applies to all YAM variants, see the YAM Arm Series page.

Specifications

Parameter	Value
Price	$4,999
Degrees of Freedom	6
Communication	CAN bus (1 Mbit/s)
Shoulder motors (joints 1–2)	2× DM6248 (vs DM4340 on YAM/Pro/Ultra)
Middle motors (joints 3–4)	2× DM4340
Wrist motors (joints 5–6)	2× DM4310
Joint 1 range	-165° to +165°
Joint 2 range	0° to +180°
Joint 3 range	0° to +173°
Joint 4 range	-97° to +90°
Joint 5 range	-90° to +90°
Joint 6 range	-120° to +120°
Payload	TBD — see i2rt.com
Reach	TBD — see i2rt.com
Weight	TBD — see i2rt.com
Build / Materials	TBD — see i2rt.com

API Usage

Pass ArmType.BIG_YAM (or the lowercase string "big_yam") to get_yam_robot():

python

from i2rt.robots.get_robot import get_yam_robot
from i2rt.robots.utils import ArmType, GripperType

robot = get_yam_robot(
    channel="can0",
    arm_type=ArmType.BIG_YAM,
    gripper_type=GripperType.LINEAR_4310,
)

Command line

bash

python i2rt/robots/motor_chain_robot.py --arm big_yam --channel can0 --gripper linear_4310

Control gains (different from YAM/Pro/Ultra)

BIG YAM ships with a different set of default gains because its shoulder motors (DM6248) and joint geometry differ:

yaml

motor_list:
  - [0x01, "DM6248"]   # vs DM4340 on YAM
  - [0x02, "DM6248"]   # vs DM4340 on YAM
  - [0x03, "DM4340"]
  - [0x04, "DM4340"]   # vs DM4310 on YAM
  - [0x05, "DM4310"]
  - [0x06, "DM4310"]

directions: [1, -1, 1, 1, 1, 1]     # only joint 2 is reversed

kp:                 [80.0, 80.0, 80.0, 40.0, 40.0, 10.0]    # kp[3], kp[4] = 40 (vs 10 on Standard)
kd:                 [5.0,  5.0,  5.0,  3.0,  1.5,  1.5]     # kd[3] = 3.0 (vs 1.5)

gravity_comp_factor:[1.0,  1.2,  1.0,  1.1,  1.0,  1.0]     # factor[1,3] differ
grav_comp_kd:       [0.5,  0.5,  0.5,  0.3,  0.1,  0.1]     # higher shoulder damping
coulomb_friction:   [0.1,  0.1,  0.3,  0.3,  0.06, 0.06]    # less stiction on shoulders

Joint direction reversed

Joint 2 is mechanically reversed on BIG YAM (directions: [1, -1, 1, 1, 1, 1]). The SDK handles this internally — command_joint_pos(q) still uses the standard convention — but raw motor commands or per-motor diagnostics will see a flipped sign on joint 2.

Don't reuse YAM/Pro/Ultra trajectories directly

Because of the reversed joint directions, trajectories recorded on a YAM Standard/Pro/Ultra will NOT play back correctly on BIG YAM without remapping. If you need a portable trajectory, record it via command_joint_pos() (logical convention) rather than raw motor values.

When to Choose BIG YAM

Task	Standard / Pro / Ultra	BIG YAM
Light pick-and-place	✅	overkill
Tabletop teleop demo	✅	overkill
Heavy / dense object lifting	⚠ may struggle	✅
Long-reach work	⚠	✅
High duty-cycle production	⚠	✅

Differences from Other YAM Variants

	Standard	Pro	Ultra	BIG YAM
`arm_type`	`YAM`	`YAM_PRO`	`YAM_ULTRA`	`BIG_YAM`
Shoulder motors	DM4340	DM4340	DM4340	DM6248
Joint 2 / 3 range	210° / 180°	210° / 180°	210° / 180°	180° / 173°
Joint directions	all `+1`	all `+1`	all `+1`	`[1, -1, 1, 1, 1, 1]`
Default PD gains	base	same	same	higher kd on J4, higher grav_comp_kd
Gravity comp factor	`[1.0,1.1,1.1,1.2,1.0,1.0]`	same	same	`[1.0,1.2,1.0,1.1,1.0,1.0]`

BIG YAM ​

Specifications ​

API Usage ​

Command line ​

Control gains (different from YAM/Pro/Ultra) ​

When to Choose BIG YAM ​

Differences from Other YAM Variants ​

See Also ​