diff --git a/omnigibson/envs/env_base.py b/omnigibson/envs/env_base.py
index 7aa9deb2e..b280f6d80 100644
--- a/omnigibson/envs/env_base.py
+++ b/omnigibson/envs/env_base.py
@@ -732,8 +732,8 @@ def default_config(self):
         return {
             # Environment kwargs
             "env": {
-                "action_frequency": 30,
-                "physics_frequency": 120,
+                "action_frequency": gm.DEFAULT_RENDERING_FREQ,
+                "physics_frequency": gm.DEFAULT_PHYSICS_FREQ,
                 "device": None,
                 "automatic_reset": False,
                 "flatten_action_space": False,
diff --git a/omnigibson/macros.py b/omnigibson/macros.py
index 8f43f074e..73d83568b 100644
--- a/omnigibson/macros.py
+++ b/omnigibson/macros.py
@@ -105,6 +105,10 @@
 gm.DEFAULT_VIEWER_WIDTH = 1280
 gm.DEFAULT_VIEWER_HEIGHT = 720
 
+# Default physics / rendering frequencies (Hz)
+gm.DEFAULT_RENDERING_FREQ = 30
+gm.DEFAULT_PHYSICS_FREQ = 120
+
 # (Demo-purpose) Whether to activate Assistive Grasping mode for Cloth (it's handled differently from RigidBody)
 gm.AG_CLOTH = False
 
diff --git a/omnigibson/robots/__init__.py b/omnigibson/robots/__init__.py
index f2a4145c8..87feadc26 100644
--- a/omnigibson/robots/__init__.py
+++ b/omnigibson/robots/__init__.py
@@ -12,5 +12,6 @@
 from omnigibson.robots.franka import FrankaPanda
 from omnigibson.robots.franka_allegro import FrankaAllegro
 from omnigibson.robots.franka_leap import FrankaLeap
+from omnigibson.robots.franka_mounted import FrankaMounted
 from omnigibson.robots.vx300s import VX300S
 from omnigibson.robots.behavior_robot import BehaviorRobot
diff --git a/omnigibson/robots/behavior_robot.py b/omnigibson/robots/behavior_robot.py
index 0e6b5428c..2212f76cb 100644
--- a/omnigibson/robots/behavior_robot.py
+++ b/omnigibson/robots/behavior_robot.py
@@ -9,6 +9,7 @@
 import omnigibson as og
 import omnigibson.lazy as lazy
 import omnigibson.utils.transform_utils as T
+from omnigibson.utils.python_utils import classproperty
 from omnigibson.macros import gm, create_module_macros
 from omnigibson.robots.locomotion_robot import LocomotionRobot
 from omnigibson.robots.manipulation_robot import ManipulationRobot, GraspingPoint
@@ -139,12 +140,12 @@ def usd_path(self):
     def model_name(self):
         return "BehaviorRobot"
 
-    @property
-    def n_arms(self):
+    @classproperty
+    def n_arms(cls):
         return 2
 
-    @property
-    def arm_names(self):
+    @classproperty
+    def arm_names(cls):
         return ["left", "right"]
 
     @property
diff --git a/omnigibson/robots/fetch.py b/omnigibson/robots/fetch.py
index e633502af..0378ed7f8 100644
--- a/omnigibson/robots/fetch.py
+++ b/omnigibson/robots/fetch.py
@@ -258,12 +258,6 @@ def _initialize(self):
         # Run super method first
         super()._initialize()
 
-        # Set the joint friction for EEF to be higher
-        for arm in self.arm_names:
-            for joint in self.finger_joints[arm]:
-                if joint.joint_type != JointType.JOINT_FIXED:
-                    joint.friction = 500
-
     def _postprocess_control(self, control, control_type):
         # Run super method first
         u_vec, u_type_vec = super()._postprocess_control(control=control, control_type=control_type)
diff --git a/omnigibson/robots/franka_mounted.py b/omnigibson/robots/franka_mounted.py
new file mode 100644
index 000000000..65eb37c7d
--- /dev/null
+++ b/omnigibson/robots/franka_mounted.py
@@ -0,0 +1,65 @@
+import os
+import numpy as np
+
+from omnigibson.macros import gm
+from omnigibson.robots.manipulation_robot import ManipulationRobot, GraspingPoint
+from omnigibson.robots.franka import FrankaPanda
+from omnigibson.utils.transform_utils import euler2quat
+
+
+class FrankaMounted(FrankaPanda):
+    """
+    The Franka Emika Panda robot mounted on a custom chassis with a custom gripper
+    """
+
+    @property
+    def model_name(self):
+        return "FrankaMounted"
+
+    @property
+    def controller_order(self):
+        return ["arm_{}".format(self.default_arm), "gripper_{}".format(self.default_arm)]
+
+    @property
+    def _default_controllers(self):
+        controllers = super()._default_controllers
+        controllers["arm_{}".format(self.default_arm)] = "InverseKinematicsController"
+        controllers["gripper_{}".format(self.default_arm)] = "MultiFingerGripperController"
+        return controllers
+
+    @property
+    def finger_lengths(self):
+        return {self.default_arm: 0.15}
+
+    @property
+    def usd_path(self):
+        return os.path.join(gm.ASSET_PATH, "models/franka/franka_mounted.usd")
+
+    @property
+    def robot_arm_descriptor_yamls(self):
+        return {self.default_arm: os.path.join(gm.ASSET_PATH, "models/franka/franka_mounted_description.yaml")}
+
+    @property
+    def urdf_path(self):
+        return os.path.join(gm.ASSET_PATH, "models/franka/franka_mounted.urdf")
+
+    @property
+    def eef_usd_path(self):
+        # TODO: Update!
+        return {self.default_arm: os.path.join(gm.ASSET_PATH, "models/franka/franka_panda_eef.usd")}
+
+    @property
+    def assisted_grasp_start_points(self):
+        return {
+            self.default_arm: [
+                GraspingPoint(link_name="panda_rightfinger", position=[0.0, 0.001, 0.045]),
+            ]
+        }
+
+    @property
+    def assisted_grasp_end_points(self):
+        return {
+            self.default_arm: [
+                GraspingPoint(link_name="panda_leftfinger", position=[0.0, 0.001, 0.045]),
+            ]
+        }
diff --git a/omnigibson/robots/husky.py b/omnigibson/robots/husky.py
index 37f302194..8ee7cd092 100644
--- a/omnigibson/robots/husky.py
+++ b/omnigibson/robots/husky.py
@@ -14,6 +14,14 @@ class Husky(LocomotionRobot):
     def _create_discrete_action_space(self):
         raise ValueError("Husky does not support discrete actions!")
 
+    @property
+    def wheel_radius(self):
+        return 0.165
+
+    @property
+    def wheel_axle_length(self):
+        return 0.670
+
     @property
     def base_control_idx(self):
         return np.array([0, 1, 2, 3])
diff --git a/omnigibson/robots/manipulation_robot.py b/omnigibson/robots/manipulation_robot.py
index 6f08f543f..cb3f7f3b3 100644
--- a/omnigibson/robots/manipulation_robot.py
+++ b/omnigibson/robots/manipulation_robot.py
@@ -478,23 +478,23 @@ def _default_controllers(self):
 
         return controllers
 
-    @property
-    def n_arms(self):
+    @classproperty
+    def n_arms(cls):
         """
         Returns:
             int: Number of arms this robot has. Returns 1 by default
         """
         return 1
 
-    @property
-    def arm_names(self):
+    @classproperty
+    def arm_names(cls):
         """
         Returns:
             list of str: List of arm names for this robot. Should correspond to the keys used to index into
                 arm- and gripper-related dictionaries, e.g.: eef_link_names, finger_link_names, etc.
                 Default is string enumeration based on @self.n_arms.
         """
-        return [str(i) for i in range(self.n_arms)]
+        return [str(i) for i in range(cls.n_arms)]
 
     @property
     def default_arm(self):
diff --git a/omnigibson/robots/tiago.py b/omnigibson/robots/tiago.py
index 26513e3a2..45bac5ef1 100644
--- a/omnigibson/robots/tiago.py
+++ b/omnigibson/robots/tiago.py
@@ -8,7 +8,7 @@
 from omnigibson.robots.active_camera_robot import ActiveCameraRobot
 from omnigibson.robots.manipulation_robot import GraspingPoint, ManipulationRobot
 from omnigibson.robots.locomotion_robot import LocomotionRobot
-from omnigibson.utils.python_utils import assert_valid_key
+from omnigibson.utils.python_utils import assert_valid_key, classproperty
 from omnigibson.utils.usd_utils import JointType
 
 # Create settings for this module
@@ -185,12 +185,12 @@ def arm_joint_names(self):
     def model_name(self):
         return "Tiago"
 
-    @property
-    def n_arms(self):
+    @classproperty
+    def n_arms(cls):
         return 2
 
-    @property
-    def arm_names(self):
+    @classproperty
+    def arm_names(cls):
         return ["left", "right"]
 
     @property
diff --git a/omnigibson/scenes/interactive_traversable_scene.py b/omnigibson/scenes/interactive_traversable_scene.py
index 646eee2cf..aa7f60749 100644
--- a/omnigibson/scenes/interactive_traversable_scene.py
+++ b/omnigibson/scenes/interactive_traversable_scene.py
@@ -138,10 +138,9 @@ def filter_rooms_and_object_categories(
                 load_room_instances = [load_room_instances]
             load_room_instances_filtered = []
             for room_instance in load_room_instances:
-                if room_instance in self._seg_map.room_ins_name_to_ins_id:
-                    load_room_instances_filtered.append(room_instance)
-                else:
+                if room_instance not in self._seg_map.room_ins_name_to_ins_id:
                     log.warning("room_instance [{}] does not exist.".format(room_instance))
+                load_room_instances_filtered.append(room_instance)
             self.load_room_instances = load_room_instances_filtered
         elif load_room_types is not None:
             if isinstance(load_room_types, str):
diff --git a/omnigibson/sensors/vision_sensor.py b/omnigibson/sensors/vision_sensor.py
index 9fd0d79ad..df6ba9a18 100644
--- a/omnigibson/sensors/vision_sensor.py
+++ b/omnigibson/sensors/vision_sensor.py
@@ -756,6 +756,9 @@ def clear(cls):
         # Render to update
         render()
 
+        cls.SEMANTIC_REMAPPER = Remapper()
+        cls.INSTANCE_REMAPPER = Remapper()
+        cls.INSTANCE_ID_REMAPPER = Remapper()
         cls.SENSORS = dict()
         cls.KNOWN_SEMANTIC_IDS = set()
         cls.KEY_ARRAY = None
diff --git a/omnigibson/simulator.py b/omnigibson/simulator.py
index a581a3914..83b1578a7 100644
--- a/omnigibson/simulator.py
+++ b/omnigibson/simulator.py
@@ -214,10 +214,12 @@ class Simulator(lazy.omni.isaac.core.simulation_context.SimulationContext, Seria
 
         Args:
             gravity (float): gravity on z direction.
-            physics_dt (float): dt between physics steps. Defaults to 1.0 / 120.0.
-            rendering_dt (float): dt between rendering steps. Note: rendering means rendering a frame of the current
-                application and not only rendering a frame to the viewports/ cameras. So UI elements of Isaac Sim will
-                be refreshed with this dt as well if running non-headless. Defaults to 1.0 / 30.0.
+            physics_dt (None or float): dt between physics steps. If None, will use default value
+                1 / gm.DEFAULT_PHYSICS_FREQ
+            rendering_dt (None or float): dt between rendering steps. Note: rendering means rendering a frame of the
+                current application and not only rendering a frame to the viewports/ cameras. So UI elements of
+                Isaac Sim will be refreshed with this dt as well if running non-headless. If None, will use default
+                value 1 / gm.DEFAULT_RENDERING_FREQ
             stage_units_in_meters (float): The metric units of assets. This will affect gravity value..etc.
                 Defaults to 0.01.
             viewer_width (int): width of the camera image, in pixels
@@ -230,8 +232,8 @@ class Simulator(lazy.omni.isaac.core.simulation_context.SimulationContext, Seria
         def __init__(
             self,
             gravity=9.81,
-            physics_dt=1.0 / 120.0,
-            rendering_dt=1.0 / 30.0,
+            physics_dt=None,
+            rendering_dt=None,
             stage_units_in_meters=1.0,
             viewer_width=gm.DEFAULT_VIEWER_WIDTH,
             viewer_height=gm.DEFAULT_VIEWER_HEIGHT,
@@ -244,8 +246,8 @@ def __init__(
 
             # Run super init
             super().__init__(
-                physics_dt=physics_dt,
-                rendering_dt=rendering_dt,
+                physics_dt=1.0 / gm.DEFAULT_PHYSICS_FREQ if physics_dt is None else physics_dt,
+                rendering_dt=1.0 / gm.DEFAULT_RENDERING_FREQ if rendering_dt is None else rendering_dt,
                 stage_units_in_meters=stage_units_in_meters,
                 device=device,
             )
@@ -1223,13 +1225,16 @@ def restore(self, json_path):
 
             return
 
-        def save(self, json_path):
+        def save(self, json_path=None):
             """
             Saves the current simulation environment to @json_path.
 
             Args:
-                json_path (str): Full path of JSON file to save (should end with .json), which contains information
-                    to recreate the current scene.
+                json_path (None or str): Full path of JSON file to save (should end with .json), which contains information
+                    to recreate the current scene, if specified. If None, will return json string insted
+
+            Returns:
+                None or str: If @json_path is None, returns dumped json string. Else, None
             """
             # Make sure the sim is not stopped, since we need to grab joint states
             assert not self.is_stopped(), "Simulator cannot be stopped when saving to USD!"
@@ -1258,11 +1263,15 @@ def save(self, json_path):
             }
 
             # Write this to the json file
-            Path(os.path.dirname(json_path)).mkdir(parents=True, exist_ok=True)
-            with open(json_path, "w+") as f:
-                json.dump(scene_info, f, cls=NumpyEncoder, indent=4)
+            if json_path is None:
+                return json.dumps(scene_info, cls=NumpyEncoder, indent=4)
+
+            else:
+                Path(os.path.dirname(json_path)).mkdir(parents=True, exist_ok=True)
+                with open(json_path, "w+") as f:
+                    json.dump(scene_info, f, cls=NumpyEncoder, indent=4)
 
-            log.info("The current simulation environment saved.")
+                log.info("The current simulation environment saved.")
 
         def _open_new_stage(self):
             """
diff --git a/omnigibson/utils/ui_utils.py b/omnigibson/utils/ui_utils.py
index a57152130..34d6cc973 100644
--- a/omnigibson/utils/ui_utils.py
+++ b/omnigibson/utils/ui_utils.py
@@ -485,7 +485,7 @@ def get_interpolated_positions(step):
                 pan_angle = np.arctan2(-xy_direction[0], xy_direction[1])
                 tilt_angle = np.arcsin(z)
                 # Infer global quat orientation from these angles
-                quat = T.euler2quat([np.pi / 2 - tilt_angle, 0.0, pan_angle])
+                quat = T.euler2quat([np.pi / 2 + tilt_angle, 0.0, pan_angle])
                 poses.append([positions[j], quat])
 
         # Record the generated trajectory