1.10/joint.sdf: better default limit values

* Use `±inf` instead of `±1e16` for position limits
* Use `inf` instead of `-1` for effort, velocity limits

Signed-off-by: Steve Peters <scpeters@openrobotics.org>

Migration.md

@@ -538,6 +538,12 @@ ABI was broken for `sdf::Element`, and restored on version 11.2.1.
 
 ### Modifications
 
+1. **joint.sdf**: axis limits default values have changed
+    + `//limit/lower`: `-inf` (formerly `-1e16`)
+    + `//limit/upper`: `inf` (formerly `1e16`)
+    + `//limit/velocity`: `inf` (formerly `-1`)
+    + `//limit/effort`: `inf` (formerly `-1`)
+
 1. **plugin.sdf**: name attribute is now optional with empty default value.
 
 ## SDFormat specification 1.8 to 1.9

sdf/1.10/joint.sdf

@@ -74,16 +74,16 @@
     </element> <!-- End Dynamics -->
     <element name="limit" required="1">
       <description>specifies the limits of this joint</description>
-      <element name="lower" type="double" default="-1e16" required="1">
+      <element name="lower" type="double" default="-inf" required="1">
         <description>Specifies the lower joint limit (radians for revolute joints, meters for prismatic joints). Omit if joint is continuous.</description>
       </element>
-      <element name="upper" type="double" default="1e16" required="1">
+      <element name="upper" type="double" default="inf" required="1">
         <description>Specifies the upper joint limit (radians for revolute joints, meters for prismatic joints). Omit if joint is continuous.</description>
       </element>
-      <element name="effort" type="double" default="-1" required="0">
+      <element name="effort" type="double" default="inf" required="0">
         <description>A value for enforcing the maximum joint effort applied. Limit is not enforced if value is negative.</description>
       </element>
-      <element name="velocity" type="double" default="-1" required="0">
+      <element name="velocity" type="double" default="inf" required="0">
         <description>A value for enforcing the maximum joint velocity.</description>
       </element>
 
@@ -132,16 +132,16 @@
 
     <element name="limit" required="1">
       <description></description>
-      <element name="lower" type="double" default="-1e16" required="0">
+      <element name="lower" type="double" default="-inf" required="0">
         <description>An attribute specifying the lower joint limit (radians for revolute joints, meters for prismatic joints). Omit if joint is continuous.</description>
       </element>
-      <element name="upper" type="double" default="1e16" required="0">
+      <element name="upper" type="double" default="inf" required="0">
         <description>An attribute specifying the upper joint limit (radians for revolute joints, meters for prismatic joints). Omit if joint is continuous.</description>
       </element>
-      <element name="effort" type="double" default="-1" required="0">
+      <element name="effort" type="double" default="inf" required="0">
         <description>An attribute for enforcing the maximum joint effort applied by Joint::SetForce.  Limit is not enforced if value is negative.</description>
       </element>
-      <element name="velocity" type="double" default="-1" required="0">
+      <element name="velocity" type="double" default="inf" required="0">
         <description>(not implemented) An attribute for enforcing the maximum joint velocity.</description>
       </element>
 

src/JointAxis.cc

@@ -16,6 +16,7 @@
  */
 #include <algorithm>
 #include <iterator>
+#include <limits>
 
 #include <gz/math/Pose3.hh>
 #include <gz/math/Vector3.hh>
@@ -60,18 +61,18 @@ class sdf::JointAxis::Implementation
 
   /// \brief Specifies the lower joint limit (radians for revolute joints,
   /// meters for prismatic joints). Omit if joint is continuous.
-  public: double lower = -1e16;
+  public: double lower = -std::numeric_limits<double>::infinity();
 
   /// \brief Specifies the upper joint limit (radians for revolute joints,
   /// meters for prismatic joints). Omit if joint is continuous.
-  public: double upper = 1e16;
+  public: double upper = std::numeric_limits<double>::infinity();
 
   /// \brief A value for enforcing the maximum joint effort applied.
   /// Limit is not enforced if value is negative.
-  public: double effort = -1;
+  public: double effort = std::numeric_limits<double>::infinity();
 
   /// \brief A value for enforcing the maximum joint velocity.
-  public: double maxVelocity = -1;
+  public: double maxVelocity = std::numeric_limits<double>::infinity();
 
   /// \brief Joint stop stiffness.
   public: double stiffness = 1e8;

src/JointAxis_TEST.cc

@@ -16,6 +16,7 @@
 */
 
 #include <gtest/gtest.h>
+#include <limits>
 #include "sdf/JointAxis.hh"
 
 /////////////////////////////////////////////////
@@ -29,8 +30,8 @@ TEST(DOMJointAxis, Construction)
   EXPECT_DOUBLE_EQ(0.0, axis.Friction());
   EXPECT_DOUBLE_EQ(0.0, axis.SpringReference());
   EXPECT_DOUBLE_EQ(0.0, axis.SpringStiffness());
-  EXPECT_DOUBLE_EQ(-1e16, axis.Lower());
-  EXPECT_DOUBLE_EQ(1e16, axis.Upper());
+  EXPECT_DOUBLE_EQ(-std::numeric_limits<double>::infinity(), axis.Lower());
+  EXPECT_DOUBLE_EQ(std::numeric_limits<double>::infinity(), axis.Upper());
   EXPECT_DOUBLE_EQ(std::numeric_limits<double>::infinity(), axis.Effort());
   EXPECT_DOUBLE_EQ(std::numeric_limits<double>::infinity(), axis.MaxVelocity());
   EXPECT_DOUBLE_EQ(1e8, axis.Stiffness());

test/integration/joint_axis_dom.cc

@@ -244,8 +244,8 @@ TEST(DOMJointAxis, InfiniteLimits)
     ASSERT_NE(nullptr, joint);
     auto axis = joint->Axis(0);
     ASSERT_NE(nullptr, axis);
-    EXPECT_DOUBLE_EQ(-1e16, axis->Lower());
-    EXPECT_DOUBLE_EQ(1e16, axis->Upper());
+    EXPECT_DOUBLE_EQ(-kInf, axis->Lower());
+    EXPECT_DOUBLE_EQ(kInf, axis->Upper());
     EXPECT_DOUBLE_EQ(kInf, axis->Effort());
     EXPECT_DOUBLE_EQ(kInf, axis->MaxVelocity());
   }